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- <chapter id="ecpg">
- <docinfo>
- <authorgroup>
- <author>
- <firstname>Linus</firstname>
- <surname>Tolke</surname>
- </author>
- <author>
- <firstname>Michael</firstname>
- <surname>Meskes</surname>
- </author>
- </authorgroup>
- <copyright>
- <year>1996-1997</year>
- <holder>Linus Tolke</holder>
- </copyright>
- <copyright>
- <year>1998</year>
- <holder>Michael Meskes</holder>
- </copyright>
- <date>Transcribed 1998-02-12</date>
- </docinfo>
-
- <title><application>ecpg</application> - Embedded <acronym>SQL</acronym>
- in <acronym>C</acronym></title>
-
- <indexterm zone="ecpg"><primary>embedded SQL</primary><secondary>in C</secondary></indexterm>
+<chapter id="ecpg">
+ <title><application>ECPG</application> - Embedded <acronym>SQL</acronym> in C</title>
+
+ <indexterm zone="ecpg"><primary>embedded SQL</primary><secondary>in C</secondary></indexterm>
+
+ <para>
+ This chapter describes the embedded <acronym>SQL</acronym> package
+ for <productname>PostgreSQL</productname>. It works with
+ <acronym>C</acronym> and <acronym>C++</acronym>. It was written by
+ Linus Tolke (<email>linus@epact.se</email>) and Michael Meskes
+ (<email>meskes@postgresql.org</email>).
+ </para>
+
+ <para>
+ Admittedly, this documentation is quite incomplete. But since this
+ interface is standardized, additional information can be found in
+ many resources about SQL.
+ </para>
+
+ <sect1 id="ecpg-concept">
+ <title>The Concept</title>
<para>
- This describes the embedded <acronym>SQL</acronym> package for
- <productname>PostgreSQL</productname>. It works with
- <acronym>C</acronym> and <acronym>C++</acronym>. It was written by
- Linus Tolke (<email>linus@epact.se</email>) and Michael Meskes
- (<email>meskes@debian.org</email>). The package is installed with the
- <productname>PostgreSQL</> distribution, and carries a similar license.
+ An embedded SQL program consists of code written in an ordinary
+ programming language, in this case C, mixed with SQL commands in
+ specially marked sections. To build the program, the source code
+ is first passed to the embedded SQL preprocessor, which converts it
+ to an ordinary C program, and afterwards it can be processed by a C
+ compilation tool chain.
</para>
- <sect1 id="ecpg-why">
- <title>Why Embedded <acronym>SQL</acronym>?</title>
+ <para>
+ Embedded <acronym>SQL</acronym> has advantages over other methods
+ for handling <acronym>SQL</acronym> commands from C code. First, it
+ takes care of the tedious passing of information to and from
+ variables in your <acronym>C</acronym> program. Secondly, embedded
+ SQL in C is defined in the SQL standard and supported by many other
+ SQL databases. The PostgreSQL implementation is designed to match
+ this standard as much as possible, and it is usually possible to
+ port embedded <acronym>SQL</acronym> programs written for other
+ <acronym>RDBMS</acronym> to <productname>PostgreSQL</productname>
+ with relative ease.
+ </para>
- <para>
- Embedded <acronym>SQL</acronym> has advantages over other methods
- for handling <acronym>SQL</acronym> queries. It takes care of
- the tedious passing of information to and from variables in your
- <acronym>C</acronym> or <acronym>C++</acronym> program. Many
- <acronym>RDBMS</acronym> packages support this embedded language.
- </para>
+ <para>
+ As indicated, programs written for the embedded SQL interface are
+ normal C programs with special code inserted to perform
+ database-related actions. This special code always has the form
+<programlisting>
+EXEC SQL ...;
+</programlisting>
+ These statements syntactically take the place of a C statement.
+ Depending on the particular statement, they may appear in the
+ global context or within a function. Embedded SQL statements
+ follow the case-sensitivity rules of normal SQL code, and not those
+ of C.
+ </para>
- <para>
- There is an ANSI standard describing how the embedded language
- should work. <application>ecpg</application> was designed to match
- this standard as much as possible. It is possible to port embedded
- <acronym>SQL</acronym> programs written for other
- <acronym>RDBMS</acronym> to <productname>PostgreSQL</productname>.
- </para>
- </sect1>
+ <para>
+ The following sections explain all the embedded SQL statements.
+ </para>
+ </sect1>
- <sect1 id="ecpg-concept">
- <title>The Concept</title>
+ <sect1 id="ecpg-connect">
+ <title>Connecting to the Database Server</title>
- <para>
- You write your program in <acronym>C/C++</acronym> with special
- <acronym>SQL</acronym> constructs. When declaring variables to be
- used in <acronym>SQL</acronym> statements, you need to put them in a
- special <command>declare</> section. You use a special syntax for the
- <acronym>SQL</acronym> queries.
- </para>
+ <para>
+ One connects to a database using the following statement:
+<programlisting>
+EXEC SQL CONNECT TO <replaceable>target</replaceable> <optional>AS <replaceable>connection-name</replaceable></optional> <optional>USER <replaceable>user-name</replaceable></optional>;
+</programlisting>
+ The <replaceable>target</replaceable> can be specified in the
+ following ways:
+
+ <itemizedlist>
+ <listitem>
+ <simpara>
+ <literal><replaceable>dbname</><optional>@<replaceable>hostname</></optional><optional>:<replaceable>port</></optional></literal>
+ </simpara>
+ </listitem>
+
+ <listitem>
+ <simpara>
+ <literal>tcp:postgresql://<replaceable>hostname</><optional>:<replaceable>port</></optional><optional>/<replaceable>dbname</></optional><optional>?<replaceable>options</></optional></literal>
+ </simpara>
+ </listitem>
+
+ <listitem>
+ <simpara>
+ <literal>unix:postgresql://<replaceable>hostname</><optional>:<replaceable>port</></optional><optional>/<replaceable>dbname</></optional><optional>?<replaceable>options</></optional></literal>
+ </simpara>
+ </listitem>
+
+ <listitem>
+ <simpara>
+ <literal><replaceable>character variable</replaceable></literal>
+ </simpara>
+ </listitem>
+
+ <listitem>
+ <simpara>
+ <literal><replaceable>character string</replaceable></literal>
+ </simpara>
+ </listitem>
+
+ <listitem>
+ <simpara>
+ <literal>DEFAULT</literal>
+ </simpara>
+ </listitem>
+ </itemizedlist>
+ </para>
- <para>
- Before compiling you run the file through the embedded
- <acronym>SQL</acronym> <acronym>C</acronym> preprocessor and it
- converts the <acronym>SQL</acronym> statements you used to function
- calls with the variables used as arguments. Both query input and
- result output variables are passed.
- </para>
+ <para>
+ There are also different ways to specify the user name:
+
+ <itemizedlist>
+ <listitem>
+ <simpara>
+ <literal><replaceable>userid</replaceable></literal>
+ </simpara>
+ </listitem>
+
+ <listitem>
+ <simpara>
+ <literal><replaceable>userid</replaceable>/<replaceable>password</replaceable></literal>
+ </simpara>
+ </listitem>
+
+ <listitem>
+ <simpara>
+ <literal><replaceable>userid</replaceable> IDENTIFIED BY <replaceable>password</replaceable></literal>
+ </simpara>
+ </listitem>
+
+ <listitem>
+ <simpara>
+ <literal><replaceable>userid</replaceable> USING <replaceable>password</replaceable></literal>
+ </simpara>
+ </listitem>
+ </itemizedlist>
+ The <replaceable>userid</replaceable> and
+ <replaceable>password</replaceable> may be a constant text, a
+ character variable, or a character string.
+ </para>
- <para>
- After compiling, you must link with a special library that contains
- needed functions. These functions fetch information from the
- arguments, perform the <acronym>SQL</acronym> query using the
- <filename>libpq</filename> interface, and put the result in the
- arguments specified for output.
- </para>
- </sect1>
+ <para>
+ The <replaceable>connection-name</replaceable> is used to handle
+ multiple connections in one program. It can be omitted if a
+ program uses only one connection.
+ </para>
+ </sect1>
- <sect1 id="ecpg-use">
- <title>How To Use <application>ecpg</application></title>
+ <sect1 id="ecpg-disconnect">
+ <title>Closing a Connection</title>
- <para>
- This section describes how to use <application>ecpg</application>.
- </para>
+ <para>
+ To close a connection, use the following statement:
+<programlisting>
+EXEC SQL DISCONNECT [<replaceable>connection</replaceable>];
+</programlisting>
+ The <replaceable>connection</replaceable> can be specified
+ in the following ways:
+
+ <itemizedlist>
+ <listitem>
+ <simpara>
+ <literal><replaceable>connection-name</replaceable></literal>
+ </simpara>
+ </listitem>
+
+ <listitem>
+ <simpara>
+ <literal>DEFAULT</literal>
+ </simpara>
+ </listitem>
+
+ <listitem>
+ <simpara>
+ <literal>CURRENT</literal>
+ </simpara>
+ </listitem>
+
+ <listitem>
+ <simpara>
+ <literal>ALL</literal>
+ </simpara>
+ </listitem>
+ </itemizedlist>
+ </para>
+ </sect1>
- <sect2>
- <title>Preprocessor</title>
+ <sect1 id="ecpg-commands">
+ <title>Running SQL Commands</title>
- <para>
- The preprocessor is called <application>ecpg</application>. After
- installation it resides in the <productname>PostgreSQL</productname>
- <filename>bin/</filename> directory.
- </para>
- </sect2>
- <sect2>
- <title>Library</title>
+ <para>
+ Any SQL command can be run from within an embedded SQL application.
+ Below are some examples of how to do that.
+ </para>
- The <application>ecpg</application> library is called
- <filename>libecpg.a</filename> or <filename>libecpg.so</filename>.
- Additionally, the library uses the <filename>libpq</filename>
- library for communication to the
- <productname>PostgreSQL</productname> server. You will have to link
- your program using <parameter>-lecpg -lpq</parameter>.
- </para>
+ <para>
+ Creating a table:
+<programlisting>
+EXEC SQL CREATE TABLE foo (number integer, ascii char(16));
+EXEC SQL CREATE UNIQUE INDEX num1 ON foo(number);
+EXEC SQL COMMIT;
+</programlisting>
+ </para>
- <para>
- The library has some methods that are <quote>hidden</quote> but may prove
- useful.
+ <para>
+ Inserting rows:
+<programlisting>
+EXEC SQL INSERT INTO foo (number, ascii) VALUES (9999, 'doodad');
+EXEC SQL COMMIT;
+</programlisting>
+ </para>
- <itemizedlist>
- <listitem>
- <para>
- <function>ECPGdebug(int <replaceable>on</replaceable>, FILE
- *<replaceable>stream</replaceable>)</function> turns on debug
- logging if called with the first argument non-zero. Debug
- logging is done on <replaceable>stream</replaceable>. Most
- <acronym>SQL</acronym> statement log their arguments and results.
- </para>
+ <para>
+ Deleting rows:
+<programlisting>
+EXEC SQL DELETE FROM foo WHERE number = 9999;
+EXEC SQL COMMIT;
+</programlisting>
+ </para>
- <para>
- The most important function , <function>ECPGdo</function>, logs
- all <acronym>SQL</acronym> statements with both the expanded
- string, i.e. the string with all the input variables inserted,
- and the result from the <productname>PostgreSQL</productname>
- server. This can be very useful when searching for errors in
- your <acronym>SQL</acronym> statements.
- </para>
- </listitem>
+ <para>
+ Singleton Select:
+<programlisting>
+EXEC SQL SELECT foo INTO :FooBar FROM table1 WHERE ascii = 'doodad';
+</programlisting>
+ </para>
- <listitem>
- <para>
- <function>ECPGstatus()</function>
- This method returns TRUE if we are connected to a database and FALSE if not.
- </para>
- </listitem>
- </itemizedlist>
- </para>
- </sect2>
+ <para>
+ Select using Cursors:
+<programlisting>
+EXEC SQL DECLARE foo_bar CURSOR FOR
+ SELECT number, ascii FROM foo
+ ORDER BY ascii;
+EXEC SQL FETCH foo_bar INTO :FooBar, DooDad;
+...
+EXEC SQL CLOSE foo_bar;
+EXEC SQL COMMIT;
+</programlisting>
+ </para>
+
+ <para>
+ Updates:
+<programlisting>
+EXEC SQL UPDATE foo
+ SET ascii = 'foobar'
+ WHERE number = 9999;
+EXEC SQL COMMIT;
+</programlisting>
+ </para>
- <sect2>
- <title>Error handling</title>
+ <para>
+ The tokens of the form
+ <literal>:<replaceable>something</replaceable></literal> are
+ <firstterm>host variables</firstterm>, that is, they refer to
+ variables in the C program. They are explained in the next
+ section.
+ </para>
- <para>
- To detect errors from the <productname>PostgreSQL</productname>
- server, include a line like:
+ <para>
+ In the default mode, statements are committed only when
+ <command>EXEC SQL COMMIT</command> is issued. The embedded SQL
+ interface also supports autocommit of transactions (as known from
+ other interfaces) via the <option>-t</option> command-line option
+ to <command>ecpg</command> (see below) or via the <literal>EXEC SQL
+ SET AUTOCOMMIT TO ON</literal> statement. In autocommit mode, each
+ query is automatically committed unless it is inside an explicit
+ transaction block. This mode can be explicitly turned off using
+ <literal>EXEC SQL SET AUTOCOMMIT TO OFF</literal>.
+ </para>
+ </sect1>
+
+ <sect1 id="ecpg-variables">
+ <title>Passing Data</title>
+
+ <para>
+ To pass data from the program to the database, for example as
+ parameters in a query, or to pass data from the database back to
+ the program, the C variables that are intended to contain this data
+ need to be declared in a specially marked section, so the embedded
+ SQL preprocessor is made aware of them.
+ </para>
+
+ <para>
+ This section starts with
<programlisting>
-exec sql include sqlca;
+EXEC SQL BEGIN DECLARE SECTION;
</programlisting>
- in the include section of your file. This will define a <type>struct</> and
- a variable with the name <varname>sqlca</varname> as follows:
+ and ends with
<programlisting>
-struct sqlca
-{
- char sqlcaid[8];
- long sqlabc;
- long sqlcode;
- struct
- {
- int sqlerrml;
- char sqlerrmc[70];
- } sqlerrm;
- char sqlerrp[8];
- long sqlerrd[6];
- /* 0: empty */
- /* 1: OID of processed tuple if applicable */
- /* 2: number of rows processed in an INSERT, UPDATE */
- /* or DELETE statement */
- /* 3: empty */
- /* 4: empty */
- /* 5: empty */
- char sqlwarn[8];
- /* 0: set to 'W' if at least one other is 'W' */
- /* 1: if 'W' at least one character string */
- /* value was truncated when it was */
- /* stored into a host variable. */
- /* 2: empty */
- /* 3: empty */
- /* 4: empty */
- /* 5: empty */
- /* 6: empty */
- /* 7: empty */
- char sqlext[8];
-} sqlca;
+EXEC SQL END DECLARE SECTION;
</programlisting>
- </para>
+ Between those lines, there must be normal C variable declarations, such as
+<programlisting>
+int x;
+char foo[16], bar[16];
+</programlisting>
+ </para>
- <para>
- If an no error occurred in the last <acronym>SQL</acronym> statement.
- <parameter>sqlca.sqlcode</parameter> will be 0 (<symbol>ECPG_NO_ERROR</>). If
- <parameter>sqlca.sqlcode</parameter> is less that zero, this is a
- serious error, like the database definition does not match the
- query. If it is greater than zero, it is a normal error like the
- table did not contain the requested row.
- </para>
+ <para>
+ The declarations are also echoed to the output file as a normal C
+ variables, so there's no need to declare them again. Variables
+ that are not intended to be used with SQL commands can be declared
+ normally outside these special sections.
+ </para>
- <parameter>sqlca.sqlerrm.sqlerrmc</parameter> will contain a string
- that describes the error. The string ends with the line number in
- the source file.
- </para>
+ <para>
+ The definition of a structure or union also must be listed inside a
+ <literal>DECLARE</> section. Otherwise the preprocessor cannot
+ handle these types since it does not know the definition.
+ </para>
- <para>
- These are the errors that can occur:
+ <para>
+ The special types <type>VARCHAR</type> and <type>VARCHAR2</type>
+ are converted into a named <type>struct</> for every variable. A
+ declaration like:
+<programlisting>
+VARCHAR var[180];
+</programlisting>
+ is converted into:
+<programlisting>
+struct varchar_var { int len; char arr[180]; } var;
+</programlisting>
+ This structure is suitable for interfacing with SQL datums of type
+ <type>VARCHAR</type>.
+ </para>
- <variablelist>
- <varlistentry>
- <term><computeroutput>-12, Out of memory in line %d.</computeroutput></term>
- <listitem>
- <para>
- Should not normally occur. This indicates your virtual memory is
- exhausted.
- </para>
- </listitem>
- </varlistentry>
+ <para>
+ To use a properly declared C variable in an SQL statement, write
+ <literal>:<replaceable>varname</></literal> where an expression is
+ expected. See the previous section for some examples.
+ </para>
+ </sect1>
- <varlistentry>
- <term><computeroutput>-200 (ECPG_UNSUPPORTED): Unsupported type %s on line %d.</computeroutput></term>
- <listitem>
- <para>
- Should not normally occur. This indicates the preprocessor has
- generated something that the library does not know about.
- Perhaps you are running incompatible versions of the
- preprocessor and the library.
- </para>
- </listitem>
- </varlistentry>
+ <sect1 id="ecpg-errors">
+ <title>Error Handling</title>
- <varlistentry>
- <term><computeroutput>-201 (ECPG_TOO_MANY_ARGUMENTS): Too many arguments line %d.</computeroutput></term>
- <listitem>
- <para>
- This means that <productname>PostgreSQL</productname> has
- returned more arguments than we have matching variables.
- Perhaps you have forgotten a couple of the host variables in
- the <command>INTO :var1,:var2</command>-list.
- </para>
- </listitem>
- </varlistentry>
+ <para>
+ The embedded SQL interface provides a simplistic and a complex way
+ to handle exceptional conditions in a program. The first method
+ causes a message to printed automatically when a certain condition
+ occurs. For example:
+<programlisting>
+EXEC SQL WHENEVER sqlerror sqlprint;
+</programlisting>
+ or
+<programlisting>
+EXEC SQL WHENEVER not found sqlprint;
+</programlisting>
+ This error handling remains enabled throughout the entire program.
+ </para>
- <varlistentry>
- <term><computeroutput>-202 (ECPG_TOO_FEW_ARGUMENTS): Too few arguments line %d.</computeroutput></term>
- <listitem>
- <para>
- This means that <productname>PostgreSQL</productname> has
- returned fewer arguments than we have host variables. Perhaps
- you have too many host variables in the <command>INTO
- :var1,:var2</command>-list.
- </para>
- </listitem>
- </varlistentry>
+ <note>
+ <para>
+ This is <emphasis>not</emphasis> an exhaustive example of usage
+ for the <command>EXEC SQL WHENEVER</command> statement. Further
+ examples of usage may be found in SQL manuals (e.g.,
+ <citetitle>The LAN TIMES Guide to SQL</> by Groff and Weinberg).
+ </para>
+ </note>
- <varlistentry>
- <term><computeroutput>-203 (ECPG_TOO_MANY_MATCHES): Too many matches line %d.</computeroutput></term>
- <listitem>
- <para>
- This means the query has returned several rows but the
- variables specified are not arrays. The
- <command>SELECT</command> command was not unique.
- </para>
- </listitem>
- </varlistentry>
+ <para>
+ For a more powerful error handling, the embedded SQL interface
+ provides a <type>struct</> and a variable with the name
+ <varname>sqlca</varname> as follows:
+<programlisting>
+struct sqlca
+{
+ char sqlcaid[8];
+ long sqlabc;
+ long sqlcode;
+ struct
+ {
+ int sqlerrml;
+ char sqlerrmc[70];
+ } sqlerrm;
+ char sqlerrp[8];
+
+ long sqlerrd[6];
+ /* 0: empty */
+ /* 1: OID of processed tuple if applicable */
+ /* 2: number of rows processed in an INSERT, UPDATE */
+ /* or DELETE statement */
+ /* 3: empty */
+ /* 4: empty */
+ /* 5: empty */
+
+ char sqlwarn[8];
+ /* 0: set to 'W' if at least one other is 'W' */
+ /* 1: if 'W' at least one character string */
+ /* value was truncated when it was */
+ /* stored into a host variable. */
+ /* 2: empty */
+ /* 3: empty */
+ /* 4: empty */
+ /* 5: empty */
+ /* 6: empty */
+ /* 7: empty */
+
+ char sqlext[8];
+} sqlca;
+</programlisting>
+ (Many of the empty fields may be used in a future release.)
+ </para>
- <varlistentry>
- <term><computeroutput>-204 (ECPG_INT_FORMAT): Not correctly formatted int type: %s line %d.</computeroutput></term>
- <listitem>
- <para>
- This means the host variable is of type <type>int</type> and
- the field in the <productname>PostgreSQL</productname> database
- is of another type and contains a value that cannot be
- interpreted as an <type>int</type>. The library uses
- <function>strtol()</function> for this conversion.
- </para>
- </listitem>
- </varlistentry>
+ <para>
+ If no error occurred in the last <acronym>SQL</acronym> statement,
+ <literal>sqlca.sqlcode</literal> will be 0
+ (<symbol>ECPG_NO_ERROR</>). If <literal>sqlca.sqlcode</literal> is
+ less that zero, this is a serious error, like the database
+ definition does not match the query. If it is greater than zero, it
+ is a normal error like the table did not contain the requested row.
+ </para>
- <varlistentry>
- <term><computeroutput>-205 (ECPG_UINT_FORMAT): Not correctly formatted unsigned type: %s line %d.</computeroutput></term>
- <listitem>
- <para>
- This means the host variable is of type <type>unsigned
- int</type> and the field in the
- <productname>PostgreSQL</productname> database is of another type
- and contains a value that cannot be interpreted as an
- <type>unsigned int</type>. The library uses
- <function>strtoul()</function> for this conversion.
- </para>
- </listitem>
- </varlistentry>
+ <para>
+ <literal>sqlca.sqlerrm.sqlerrmc</literal> will contain a string
+ that describes the error. The string ends with the line number in
+ the source file.
+ </para>
- <varlistentry>
- <term><computeroutput>-206 (ECPG_FLOAT_FORMAT): Not correctly formatted floating-point type: %s line %d.</computeroutput></term>
- <listitem>
- <para>
- This means the host variable is of type <type>float</type> and
- the field in the <productname>PostgreSQL</productname> database
- is of another type and contains a value that cannot be
- interpreted as a <type>float</type>. The library uses
- <function>strtod()</function> for this conversion.
- </para>
- </listitem>
- </varlistentry>
+ <para>
+ These are the errors that can occur:
+
+ <variablelist>
+ <varlistentry>
+ <term><computeroutput>-12, Out of memory in line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ Should not normally occur. This indicates your virtual memory
+ is exhausted.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-200 (ECPG_UNSUPPORTED): Unsupported type %s on line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ Should not normally occur. This indicates the preprocessor has
+ generated something that the library does not know about.
+ Perhaps you are running incompatible versions of the
+ preprocessor and the library.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-201 (ECPG_TOO_MANY_ARGUMENTS): Too many arguments line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ This means that the server has returned more arguments than we
+ have matching variables. Perhaps you have forgotten a couple
+ of the host variables in the <command>INTO
+ :var1,:var2</command> list.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-202 (ECPG_TOO_FEW_ARGUMENTS): Too few arguments line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ This means that the server has returned fewer arguments than we
+ have host variables. Perhaps you have too many host variables
+ in the <command>INTO :var1,:var2</command> list. </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-203 (ECPG_TOO_MANY_MATCHES): Too many matches line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ This means the query has returned several rows but the
+ variables specified are not arrays. The
+ <command>SELECT</command> command was not unique.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-204 (ECPG_INT_FORMAT): Not correctly formatted int type: %s line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ This means the host variable is of type <type>int</type> and
+ the field in the <productname>PostgreSQL</productname> database
+ is of another type and contains a value that cannot be
+ interpreted as an <type>int</type>. The library uses
+ <function>strtol()</function> for this conversion.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-205 (ECPG_UINT_FORMAT): Not correctly formatted unsigned type: %s line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ This means the host variable is of type <type>unsigned
+ int</type> and the field in the
+ <productname>PostgreSQL</productname> database is of another
+ type and contains a value that cannot be interpreted as an
+ <type>unsigned int</type>. The library uses
+ <function>strtoul()</function> for this conversion.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-206 (ECPG_FLOAT_FORMAT): Not correctly formatted floating-point type: %s line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ This means the host variable is of type <type>float</type> and
+ the field in the <productname>PostgreSQL</productname> database
+ is of another type and contains a value that cannot be
+ interpreted as a <type>float</type>. The library uses
+ <function>strtod()</function> for this conversion.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-207 (ECPG_CONVERT_BOOL): Unable to convert %s to bool on line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ This means the host variable is of type <type>bool</type> and
+ the field in the <productname>PostgreSQL</productname> database
+ is neither <literal>'t'</> nor <literal>'f'</>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-208 (ECPG_EMPTY): Empty query line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ The query was empty. (This cannot normally happen in an
+ embedded SQL program, so it may point to an internal error.)
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-209 (ECPG_MISSING_INDICATOR): NULL value without indicator in line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ A null value was returned and no null indicator variable was
+ supplied.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-210 (ECPG_NO_ARRAY): Variable is not an array in line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ An ordinary variable was used in a place that requires an
+ array.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-211 (ECPG_DATA_NOT_ARRAY): Data read from backend is not an array in line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ The database returned an ordinary variable in a place that
+ requires array value.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-220 (ECPG_NO_CONN): No such connection %s in line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ The program tried to access a connection that does not exist.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-221 (ECPG_NOT_CONN): Not connected in line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ The program tried to access a connection that does exist but is
+ not open.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-230 (ECPG_INVALID_STMT): Invalid statement name %s in line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ The statement you are trying to use has not been prepared.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-240 (ECPG_UNKNOWN_DESCRIPTOR): Descriptor %s not found in line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ The descriptor specified was not found. The statement you are
+ trying to use has not been prepared.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-241 (ECPG_INVALID_DESCRIPTOR_INDEX): Descriptor index out of range in line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ The descriptor index specified was out of range.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-242 (ECPG_UNKNOWN_DESCRIPTOR_ITEM): Descriptor %s not found in line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ The descriptor specified was not found. The statement you are trying to use has not been prepared.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-243 (ECPG_VAR_NOT_NUMERIC): Variable is not a numeric type in line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ The database returned a numeric value and the variable was not
+ numeric.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-244 (ECPG_VAR_NOT_CHAR): Variable is not a character type in line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ The database returned a non-numeric value and the variable was
+ numeric.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-400 (ECPG_PGSQL): Postgres error: %s line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ Some <productname>PostgreSQL</productname> error. The message
+ contains the error message from the
+ <productname>PostgreSQL</productname> backend.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-401 (ECPG_TRANS): Error in transaction processing line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ <productname>PostgreSQL</productname> signaled that we cannot
+ start, commit, or rollback the transaction.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>-402 (ECPG_CONNECT): Could not connect to database %s in line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ The connect to the database did not work.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><computeroutput>100 (ECPG_NOT_FOUND): Data not found line %d.</computeroutput></term>
+ <listitem>
+ <para>
+ This is a <quote>normal</quote> error that tells you that what
+ you are querying cannot be found or you are at the end of the
+ cursor.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </para>
+ </sect1>
- <varlistentry>
- <term><computeroutput>-207 (ECPG_CONVERT_BOOL): Unable to convert %s to bool on line %d.</computeroutput></term>
- <listitem>
- <para>
- This means the host variable is of type <type>bool</type> and
- the field in the <productname>PostgreSQL</productname> database
- is neither <literal>'t'</> nor <literal>'f'</>.
- </para>
- </listitem>
- </varlistentry>
+ <sect1 id="ecpg-include">
+ <title>Including Files</title>
- <varlistentry>
- <term><computeroutput>-208 (ECPG_EMPTY): Empty query line %d.</computeroutput></term>
- <listitem>
- <para>
- <productname>PostgreSQL</productname> returned <symbol>PGRES_EMPTY_QUERY</symbol>, probably
- because the query indeed was empty.
- </para>
- </listitem>
- </varlistentry>
+ <para>
+ To include an external file into your embedded SQL program, use:
+<programlisting>
+EXEC SQL INCLUDE <replaceable>filename</replaceable>;
+</programlisting>
+ The embedded SQL preprocessor will look for a file named
+ <literal><replaceable>filename</replaceable>.h</literal>,
+ preprocess it, and include it in the resulting C output. Thus,
+ embedded SQL statements in the included file are handled correctly.
+ </para>
- <varlistentry>
- <term><computeroutput>-209 (ECPG_MISSING_INDICATOR): NULL value without indicator in line %d.</computeroutput></term>
- <listitem>
- <para>
- <productname>PostgreSQL</productname> returned <symbol>ECPG_MISSING_INDICATOR</symbol>
- because a NULL was returned and no NULL indicator variable was supplied.
- </para>
- </listitem>
- </varlistentry>
+ <para>
+ Note that this is <emphasis>not</emphasis> the same as
+<programlisting>
+#include <<replaceable>filename</replaceable>.h>
+</programlisting>
+ because the file would not be subject to SQL command preprocessing.
+ Naturally, you can continue to use the C
+ <literal>#include</literal> directive to include other header
+ files.
+ </para>
- <varlistentry>
- <term><computeroutput>-210 (ECPG_NO_ARRAY): Variable is not an array in line %d.</computeroutput></term>
- <listitem>
- <para>
- <productname>PostgreSQL</productname> returned <symbol>ECPG_NO_ARRAY</symbol>
- because an ordinary variable was used in a place that requires
- an array.
- </para>
- </listitem>
- </varlistentry>
+ <note>
+ <para>
+ The include file name is case-sensitive, even though the rest of
+ the <literal>EXEC SQL INCLUDE</literal> command follows the normal
+ SQL case-sensitivity rules.
+ </para>
+ </note>
+ </sect1>
- <varlistentry>
- <term><computeroutput>-211 (ECPG_DATA_NOT_ARRAY): Data read from backend is not an array in line %d.</computeroutput></term>
- <listitem>
- <para>
- <productname>PostgreSQL</productname> returned <symbol>ECPG_DATA_NOT_ARRAY</symbol>
- because the database returned an ordinary variable in a place
- that requires array value.
- </para>
- </listitem>
- </varlistentry>
+ <sect1 id="ecpg-process">
+ <title>Processing Embedded SQL Programs</title>
- <varlistentry>
- <term><computeroutput>-220 (ECPG_NO_CONN): No such connection %s in line %d.</computeroutput></term>
- <listitem>
- <para>
- The program tried to access a connection that does not exist.
- </para>
- </listitem>
- </varlistentry>
+ <para>
+ Now that you have an idea how to form embedded SQL C programs, you
+ probably want to know how to compile them. Before compiling you
+ run the file through the embedded <acronym>SQL</acronym>
+ <acronym>C</acronym> preprocessor, which converts the
+ <acronym>SQL</acronym> statements you used to special function
+ calls. After compiling, you must link with a special library that
+ contains the needed functions. These functions fetch information
+ from the arguments, perform the <acronym>SQL</acronym> query using
+ the <application>libpq</application> interface, and put the result
+ in the arguments specified for output.
+ </para>
- <varlistentry>
- <term><computeroutput>-221 (ECPG_NOT_CONN): Not connected in line %d.</computeroutput></term>
- <listitem>
- <para>
- The program tried to access a connection that does exist but is
- not open.
- </para>
- </listitem>
- </varlistentry>
+ <para>
+ The preprocessor program is called <filename>ecpg</filename> and is
+ included in a normal PostgreSQL installation. Embedded SQL
+ programs are typically named with an extension
+ <filename>.pgc</filename>. If you have a program file called
+ <filename>prog1.pgc</filename>, you can preprocess it by simply
+ calling
+<programlisting>
+ecpg prog1.pgc
+</programlisting>
+ This will create a file called <filename>prog1.c</filename>. If
+ your input files do not follow the suggested naming pattern, you
+ can specify the output file explicitly using the
+ <option>-o</option> option.
+ </para>
- <varlistentry>
- <term><computeroutput>-230 (ECPG_INVALID_STMT): Invalid statement name %s in line %d.</computeroutput></term>
- <listitem>
- <para>
- The statement you are trying to use has not been prepared.
- </para>
- </listitem>
- </varlistentry>
+ <para>
+ The preprocessed file can be compiled normally, for example
+<programlisting>
+cc -c prog1.c
+</programlisting>
+ The generated C source files include headers files from the
+ PostgreSQL installation, so if you installed PostgreSQL in a
+ location that is not searched by default, you have to add an option
+ such as <literal>-I/usr/local/pgsql/include</literal> to the
+ compilation command line.
+ </para>
- <varlistentry>
- <term><computeroutput>-240 (ECPG_UNKNOWN_DESCRIPTOR): Descriptor %s not found in line %d.</computeroutput></term>
- <listitem>
- <para>
- The descriptor specified was not found. The statement you are trying to use has not been prepared.
- </para>
- </listitem>
- </varlistentry>
+ <para>
+ To link an embedded SQL program, you need to include the
+ <filename>libecpg</filename> library, like so:
+<programlisting>
+cc -o myprog prog1.o prog2.o ... -lecpg
+</programlisting>
+ Again, you might have to add an option like
+ <literal>-L/usr/local/pgsql/lib</literal> to that command line.
+ </para>
- <varlistentry>
- <term><computeroutput>-241 (ECPG_INVALID_DESCRIPTOR_INDEX): Descriptor index out of range in line %d.</computeroutput></term>
- <listitem>
- <para>
- The descriptor index specified was out of range.
- </para>
- </listitem>
- </varlistentry>
+ <para>
+ If you manage the build process of a larger project using
+ <application>make</application>, it may be convenient to include
+ the following implicit rule to your makefiles:
+<programlisting>
+ECPG = ecpg
- <varlistentry>
- <term><computeroutput>-242 (ECPG_UNKNOWN_DESCRIPTOR_ITEM): Descriptor %s not found in line %d.</computeroutput></term>
- <listitem>
- <para>
- The descriptor specified was not found. The statement you are trying to use has not been prepared.
- </para>
- </listitem>
- </varlistentry>
+%.c: %.pgc
+ $(ECPG) $<
+</programlisting>
+ </para>
- <varlistentry>
- <term><computeroutput>-243 (ECPG_VAR_NOT_NUMERIC): Variable is not a numeric type in line %d.</computeroutput></term>
- <listitem>
- <para>
- The database returned a numeric value and the variable was not
- numeric.
- </para>
- </listitem>
- </varlistentry>
+ <para>
+ The complete syntax of the <command>ecpg</command> command is
+ detailed in &cite-reference;.
+ </para>
+ </sect1>
- <varlistentry>
- <term><computeroutput>-244 (ECPG_VAR_NOT_CHAR): Variable is not a character type in line %d.</computeroutput></term>
- <listitem>
- <para>
- The database returned a non-numeric value and the variable was
- numeric.
- </para>
- </listitem>
- </varlistentry>
+ <sect1 id="ecpg-library">
+ <title>Library Functions</title>
- <varlistentry>
- <term><computeroutput>-400 (ECPG_PGSQL): Postgres error: %s line %d.</computeroutput></term>
- <listitem>
- <para>
- Some <productname>PostgreSQL</productname> error.
- The message contains the error message from the
- <productname>PostgreSQL</productname> backend.
- </para>
- </listitem>
- </varlistentry>
+ <para>
+ The <filename>libecpg</filename> library primarily contains
+ <quote>hidden</quote> functions that are used to implement the
+ functionality expressed by the embedded SQL commands. But there
+ are some functions that can usefully be called directly. Note that
+ this makes your code unportable.
+ </para>
- <varlistentry>
- <term><computeroutput>-401 (ECPG_TRANS): Error in transaction processing line %d.</computeroutput></term>
- <listitem>
- <para>
- <productname>PostgreSQL</productname> signaled that we cannot start,
- commit or rollback the transaction.
- </para>
- </listitem>
- </varlistentry>
+ <itemizedlist>
+ <listitem>
+ <para>
+ <function>ECPGdebug(int <replaceable>on</replaceable>, FILE
+ *<replaceable>stream</replaceable>)</function> turns on debug
+ logging if called with the first argument non-zero. Debug logging
+ is done on <replaceable>stream</replaceable>. Most
+ <acronym>SQL</acronym> statement log their arguments and results.
+ </para>
- <varlistentry>
- <term><computeroutput>-402 (ECPG_CONNECT): Could not connect to database %s in line %d.</computeroutput></term>
- <listitem>
- <para>
- The connect to the database did not work.
- </para>
- </listitem>
- </varlistentry>
+ <para>
+ The most important function, <function>ECPGdo</function>, logs
+ all <acronym>SQL</acronym> statements with both the expanded
+ string, i.e. the string with all the input variables inserted,
+ and the result from the <productname>PostgreSQL</productname>
+ server. This can be very useful when searching for errors in your
+ <acronym>SQL</acronym> statements.
+ </para>
+ </listitem>
- <varlistentry>
- <term><computeroutput>100 (ECPG_NOT_FOUND): Data not found line %d.</computeroutput></term>
- <listitem>
- <para>
- This is a <quote>normal</quote> error that tells you that what you are querying cannot
- be found or you are at the end of the cursor.
- </para>
- </listitem>
- </varlistentry>
-
- </variablelist>
+ <listitem>
+ <para>
+ <function>ECPGstatus()</function> This method returns true if we
+ are connected to a database and false if not.
</para>
- </sect2>
- </sect1>
+ </listitem>
+ </itemizedlist>
+ </sect1>
- <sect1 id="ecpg-limitations">
- <title>Limitations</title>
+ <sect1 id="ecpg-porting">
+ <title>Porting From Other <acronym>RDBMS</acronym> Packages</title>
- <para>
- What will never be included and why it cannot be done:
+ <para>
+ The design of <application>ecpg</application> follows the SQL
+ standard. Porting from a standard RDBMS should not be a problem.
+ Unfortunately there is no such thing as a standard RDBMS. Therefore
+ <application>ecpg</application> tries to understand syntax
+ extensions as long as they do not create conflicts with the
+ standard.
+ </para>
- <variablelist>
- <varlistentry>
- <term>Oracle's single tasking</term>
- <listitem>
- <para>
- Oracle version 7.0 on <systemitem class="osname">AIX</> 3 uses OS-supported locks in shared
- memory that allow an application designer to link an application
- in a <quote>single tasking</quote> way. Instead of starting one client
- process per application process, both the database part and the
- application part run in the same process. In later versions of
- Oracle this is no longer supported.
- </para>
+ <para>
+ The following list shows all the known incompatibilities. If you
+ find one not listed please notify the developers. Note, however,
+ that we list only incompatibilities from a preprocessor of another
+ RDBMS to <application>ecpg</application> and not
+ <application>ecpg</application> features that these RDBMS do not
+ support.
+ </para>
- <para>
- This would require a total redesign of the
- <productname>PostgreSQL</productname> access model and the
- performance gain does not justify the effort.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </sect1>
+ <variablelist>
+ <varlistentry>
+ <term>Syntax of <command>FETCH</command></term>
+ <indexterm><primary>FETCH</><secondary>embedded SQL</></indexterm>
+
+ <listitem>
+ <para>
+ The standard syntax for <command>FETCH</command> is:
+<synopsis>
+FETCH <optional><replaceable>direction</></> <optional><replaceable>amount</></> IN|FROM <replaceable>cursor</replaceable>
+</synopsis>
+ <indexterm><primary>Oracle</></>
+ <application>Oracle</application>, however, does not use the
+ keywords <literal>IN</literal> or <literal>FROM</literal>. This
+ feature cannot be added since it would create parsing conflicts.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </sect1>
+
+ <sect1 id="ecpg-develop">
+ <title>For the Developer</title>
+
+ <para>
+ This section explain how <application>ecpg</application> works
+ internally. This information can occasionally be useful to help
+ users understand how to use <application>ecpg</application>.
+ </para>
- <sect1 id="ecpg-porting">
- <title>Porting From Other <acronym>RDBMS</acronym> Packages</title>
+ <sect2>
+ <title>The Preprocessor</title>
<para>
- The design of <application>ecpg</application> follows the SQL
- standard. Porting from a standard RDBMS should not be a problem.
- Unfortunately there is no such thing as a standard RDBMS. Therefore
- <application>ecpg</application> tries to understand syntax
- extensions as long as they do not create conflicts with the
- standard.
+ The first four lines written by <command>ecpg</command> to the
+ output are fixed lines. Two are comments and two are include
+ lines necessary to interface to the library. Then the
+ preprocessor reads through the file and writes output. Normally
+ it just echoes everything to the output.
</para>
<para>
- The following list shows all the known incompatibilities. If you
- find one not listed please notify the developers. Note, however, that
- we list only incompatibilities from a precompiler of another RDBMS
- to <application>ecpg</application> and not
- <application>ecpg</application> features that these RDBMS do not
- support.
+ When it sees an <command>EXEC SQL</command> statement, it
+ intervenes and changes it. The command starts with <command>exec
+ sql</command> and ends with <command>;</command>. Everything in
+ between is treated as an <acronym>SQL</acronym> statement and
+ parsed for variable substitution.
</para>
<para>
- <variablelist>
- <varlistentry>
- <term>Syntax of FETCH</term>
- <indexterm><primary>FETCH</><secondary>embedded SQL</></indexterm>
- <listitem>
- <para>
- The standard syntax for FETCH is:
- </para>
- <para>
- FETCH [direction] [amount] IN|FROM <replaceable>cursor</replaceable>.
- </para>
- <para>
- <indexterm><primary>Oracle</></>
- <application>Oracle</application>, however, does not use the keywords IN
- or FROM. This feature cannot be added since it would create parsing
- conflicts.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
+ Variable substitution occurs when a symbol starts with a colon
+ (<literal>:</literal>). The variable with that name is looked up
+ among the variables that were previously declared within a
+ <literal>EXEC SQL DECLARE</> section. Depending on whether the
+ variable is being use for input or output, a pointer to the
+ variable is output to allow access by the function.
</para>
- </sect1>
-
- <sect1 id="ecpg-develop">
- <title>For the Developer</title>
<para>
- This section explain how <application>ecpg</application>
- works internally. It contains valuable information to help users
- understand how to use <application>ecpg</application>.
+ For every variable that is part of the <acronym>SQL</acronym>
+ query, the function gets other arguments:
+
+ <itemizedlist>
+ <listitem>
+ <para>
+ The type as a special symbol.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ A pointer to the value or a pointer to the pointer.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ The size of the variable if it is a <type>char</type> or <type>varchar</type>.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ The number of elements in the array (for array fetches).
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ The offset to the next element in the array (for array fetches).
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ The type of the indicator variable as a special symbol.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ A pointer to the value of the indicator variable or a pointer
+ to the pointer of the indicator variable.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ 0
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ Number of elements in the indicator array (for array fetches).
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ The offset to the next element in the indicator array (for
+ array fetches).
+ </para>
+ </listitem>
+ </itemizedlist>
</para>
- <sect2>
- <title>The Preprocessor</title>
-
- <para>
- The first four lines written by <command>ecpg</command> to the output are fixed lines.
- Two are comments and two are include lines necessary to interface
- to the library.
- </para>
-
- <para>
- Then the preprocessor reads through the file and writes output.
- Normally it just echoes everything to the output.
- </para>
-
- <para>
- When it sees an <command>EXEC SQL</command> statement, it
- intervenes and changes it. The <command>EXEC SQL</command>
- statement can be one of these:
-
- <variablelist>
- <varlistentry>
- <term>Declare sections</term>
- <listitem>
- <para>
- <command>Declare</> sections begin with:
-<programlisting>
-exec sql begin declare section;
-</programlisting>
- and end with:
-<programlisting>
-exec sql end declare section;
-</programlisting>
- In this section only variable declarations are allowed. Every
- variable declared within this section is stored in a list
- of variables indexed by name together with its corresponding
- type.
- </para>
-
- <para>
- In particular the definition of a structure or union also must
- be listed inside a <command>declare</> section. Otherwise
- <application>ecpg</application> cannot handle these types since
- it does not know the definition.
- </para>
-
- <para>
- The declaration is also echoed to the file to make it a normal
- C variable.
- </para>
-
- <para>
- The special types <type>VARCHAR</type> and
- <type>VARCHAR2</type> are converted into a named <type>struct</> for
- every variable. A declaration like:
-<programlisting>
-VARCHAR var[180];
-</programlisting>
- is converted into:
-<programlisting>
-struct varchar_var { int len; char arr[180]; } var;
-</programlisting>
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>Include statements</term>
- <listitem>
- <para>
- An include statement looks like:
-<programlisting>
-exec sql include filename;
-</programlisting>
- Note that this is NOT the same as:
-<programlisting>
-#include <filename.h>
-</programlisting>
- </para>
-
- <para>
- Instead the file specified is parsed by
- <application>ecpg</application> so the contents of the file are
- included in the resulting C code. This way you are able to
- specify EXEC SQL commands in an include file.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>Connect statement</term>
- <listitem>
- <para>
- A connect statement looks like:
-<programlisting>
-exec sql connect to <replaceable>connection target</replaceable>;
-</programlisting>
- It creates a connection to the specified database.
- </para>
-
- <para>
- The <replaceable>connection target</replaceable> can be specified in the
- following ways:
- <itemizedlist>
- <listitem>
- <simpara>
- <literal>dbname[@server][:port][as <replaceable>connection
- name</replaceable>][user <replaceable>user name</replaceable>]</literal>
- </simpara>
- </listitem>
-
- <listitem>
- <simpara>
- <literal>tcp:postgresql://server[:port][/dbname][as
- <replaceable>connection name</replaceable>][user <replaceable>user name</replaceable>]</literal>
- </simpara>
- </listitem>
-
- <listitem>
- <simpara>
- <literal>unix:postgresql://server[:port][/dbname][as
- <replaceable>connection name</replaceable>][user <replaceable>user name</replaceable>]</literal>
- </simpara>
- </listitem>
-
- <listitem>
- <simpara>
- <literal><replaceable>character variable</replaceable>[as
- <replaceable>connection name</replaceable>][user <replaceable>user name</replaceable>]</literal>
- </simpara>
- </listitem>
-
- <listitem>
- <simpara>
- <literal><replaceable>character string</replaceable>[as
- <replaceable>connection name</replaceable>][<replaceable>user</replaceable>]</literal>
- </simpara>
- </listitem>
-
- <listitem>
- <simpara>
- <literal>default</literal>
- </simpara>
- </listitem>
-
- <listitem>
- <simpara>
- <literal>user</literal>
- </simpara>
- </listitem>
- </itemizedlist>
- </para>
-
- <para>
- There are also different ways to specify the user name:
-
- <itemizedlist>
- <listitem>
- <simpara>
- <literal><replaceable>userid</replaceable></literal>
- </simpara>
- </listitem>
-
- <listitem>
- <simpara>
- <literal><replaceable>userid</replaceable>/<replaceable>password</replaceable></literal>
- </simpara>
- </listitem>
-
- <listitem>
- <simpara>
- <literal><replaceable>userid</replaceable> identified by <replaceable>password</replaceable></literal>
- </simpara>
- </listitem>
-
- <listitem>
- <simpara>
- <literal><replaceable>userid</replaceable> using <replaceable>password</replaceable></literal>
- </simpara>
- </listitem>
- </itemizedlist>
- </para>
-
- <para>
- Finally, the <replaceable>userid</replaceable> and <replaceable>password</replaceable> may be a constant text, a
- character variable, or a character string.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>Disconnect statements</term>
- <listitem>
- <para>
- A disconnect statement looks like:
- <programlisting>
-exec sql disconnect [<replaceable>connection target</replaceable>];
- </programlisting>
- It closes the connection to the specified database.
- </para>
-
- <para>
- The <replaceable>connection target</replaceable> can be specified in the
- following ways:
-
- <itemizedlist>
- <listitem>
- <simpara>
- <literal><replaceable>connection name</replaceable></literal>
- </simpara>
- </listitem>
-
- <listitem>
- <simpara>
- <literal>default</literal>
- </simpara>
- </listitem>
-
- <listitem>
- <simpara>
- <literal>current</literal>
- </simpara>
- </listitem>
-
- <listitem>
- <simpara>
- <literal>all</literal>
- </simpara>
- </listitem>
- </itemizedlist>
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>Open cursor statement</term>
- <listitem>
- <para>
- An open cursor statement looks like:
-<programlisting>
-exec sql open <replaceable>cursor</replaceable>;
-</programlisting>
- and is not copied to the output. Instead, the cursor's
- <command>DECLARE</> command is used because it opens the cursor
- as well.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>Commit statement</term>
- <listitem>
- <para>
- A commit statement looks like:
-<programlisting>
-exec sql commit;
-</programlisting>
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>Rollback statement</term>
- <listitem>
- <para>
- A rollback statement looks like:
+ <para>
+ Note that not all SQL commands are treated in this way. For
+ instance, an open cursor statement like
<programlisting>
-exec sql rollback;
+EXEC SQL OPEN <replaceable>cursor</replaceable>;
</programlisting>
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>Other statements</term>
- <listitem>
- <para>
- Other <acronym>SQL</acronym> statements are used by
- starting with <command>exec sql</command> and ending with
- <command>;</command>. Everything in between is treated as an
- <acronym>SQL</acronym> statement and parsed for variable
- substitution.
- </para>
-
- <para>
- Variable substitution occurs when a symbol starts with a colon
- (<command>:</command>). The variable with that name is looked
- up among the variables that were previously declared within a
- <command>declare</> section. Depending on whether the variable is
- being use for input or output, a pointer to the variable is
- output to allow access by the function.
- </para>
-
- <para>
- For every variable that is part of the <acronym>SQL</acronym>
- query, the function gets other arguments:
-
- <itemizedlist>
- <listitem>
- <para>
- The type as a special symbol.
- </para>
- </listitem>
-
- <listitem>
- <para>
- A pointer to the value or a pointer to the pointer.
- </para>
- </listitem>
-
- <listitem>
- <para>
- The size of the variable if it is a <type>char</type> or <type>varchar</type>.
- </para>
- </listitem>
-
- <listitem>
- <para>
- The number of elements in the array (for array fetches).
- </para>
- </listitem>
-
- <listitem>
- <para>
- The offset to the next element in the array (for array fetches).
- </para>
- </listitem>
-
- <listitem>
- <para>
- The type of the indicator variable as a special symbol.
- </para>
- </listitem>
-
- <listitem>
- <para>
- A pointer to the value of the indicator variable or a pointer to the pointer of the indicator variable.
- </para>
- </listitem>
-
- <listitem>
- <para>
- 0.
- </para>
- </listitem>
-
- <listitem>
- <para>
- Number of elements in the indicator array (for array fetches).
- </para>
- </listitem>
-
- <listitem>
- <para>
- The offset to the next element in the indicator array (for
- array fetches).
- </para>
- </listitem>
- </itemizedlist>
- </para>
-
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
- </sect2>
-
- <sect2>
- <title>A Complete Example</title>
+ is not copied to the output. Instead, the cursor's
+ <command>DECLARE</> command is used because it opens the cursor as
+ well.
+ </para>
- <para>
- Here is a complete example describing the output of the preprocessor of a
- file <filename>foo.pgc</filename>:
+ <para>
+ Here is a complete example describing the output of the
+ preprocessor of a file <filename>foo.pgc</filename> (details may
+ change with each particular version of the preprocessor):
<programlisting>
-exec sql begin declare section;
+EXEC SQL BEGIN DECLARE SECTION;
int index;
int result;
-exec sql end declare section;
+EXEC SQL END DECLARE SECTION;
...
-exec sql select res into :result from mytable where index = :index;
+EXEC SQL SELECT res INTO :result FROM mytable WHERE index = :index;
</programlisting>
- is translated into:
+ is translated into:
<programlisting>
/* Processed by ecpg (2.6.0) */
/* These two include files are added by the preprocessor */
int result;
/* exec sql end declare section */
...
-ECPGdo(__LINE__, NULL, "select res from mytable where index = ? ",
+ECPGdo(__LINE__, NULL, "SELECT res FROM mytable WHERE index = ? ",
ECPGt_int,&(index),1L,1L,sizeof(int),
ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EOIT,
ECPGt_int,&(result),1L,1L,sizeof(int),
ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
#line 147 "foo.pgc"
</programlisting>
- (The indentation in this manual is added for readability and not
- something the preprocessor does.)
- </para>
- </sect2>
+ (The indentation in this manual is added for readability and not
+ something the preprocessor does.)
+ </para>
+ </sect2>
- <sect2>
- <title>The Library</title>
+ <sect2>
+ <title>The Library</title>
- <para>
- The most important function in the library is
- <function>ECPGdo</function>. It takes a variable number of
- arguments. Hopefully there are no computers that limit the
- number of variables that can be accepted by a <function>varargs()</function> function. This
- can easily add up to 50 or so arguments.
- </para>
+ <para>
+ The most important function in the library is
+ <function>ECPGdo</function>. It takes a variable number of
+ arguments. Hopefully there are no computers that limit the number
+ of variables that can be accepted by a
+ <function>varargs()</function> function. This can easily add up to
+ 50 or so arguments.
+ </para>
- The arguments are:
+ <para>
+ The arguments are:
- <variablelist>
- <varlistentry>
- <term>A line number</term>
- <listitem>
- <para>
- This is a line number of the original line; used in error messages only.
- </para>
- </listitem>
- </varlistentry>
+ <variablelist>
+ <varlistentry>
+ <term>A line number</term>
+ <listitem>
+ <para>
+ This is a line number of the original line; used in error
+ messages only.
+ </para>
+ </listitem>
+ </varlistentry>
- <varlistentry>
- <term>A string</term>
- <listitem>
-
This is the <acronym>SQL</acronym> query that is to be issued.
- It is modified by the input variables, i.e. the variables that
- where not known at compile time but are to be entered in the
- query. Where the variables should go the string contains
- <literal>?</literal>.
- </para>
- </listitem>
- </varlistentry>
+ <varlistentry>
+ <term>A string</term>
+ <listitem>
+ <para>
+ This is the <acronym>SQL</acronym> query that is to be issued.
+ It is modified by the input variables, i.e. the variables that
+ where not known at compile time but are to be entered in the
+ query. Where the variables should go the string contains
+ <literal>?</literal>.
+ </para>
+ </listitem>
+ </varlistentry>
- <varlistentry>
- <term>Input variables</term>
- <listitem>
- As described in the section about the preprocessor, every input variable
- gets ten arguments.
- </para>
- </listitem>
- </varlistentry>
+ <varlistentry>
+ <term>Input variables</term>
+ <listitem>
+ <para>
+ As described in the section about the preprocessor, every
+ input variable gets ten arguments.
+ </para>
+ </listitem>
+ </varlistentry>
- <varlistentry>
- <term><parameter>ECPGt_EOIT</></term>
- <listitem>
- <para>
- An <type>enum</> telling that there are no more input variables.
- </para>
- </listitem>
- </varlistentry>
+ <varlistentry>
+ <term><parameter>ECPGt_EOIT</></term>
+ <listitem>
+ <para>
+ An <type>enum</> telling that there are no more input
+ variables.
+ </para>
+ </listitem>
+ </varlistentry>
- <varlistentry>
- <term>Output variables</term>
- <listitem>
- <para>
- As described in the section about the preprocessor, every input variable
- gets ten arguments. These variables are filled by the function.
- </para>
- </listitem>
- </varlistentry>
+ <varlistentry>
+ <term>Output variables</term>
+ <listitem>
+ <para>
+ As described in the section about the preprocessor, every
+ input variable gets ten arguments. These variables are filled
+ by the function.
+ </para>
+ </listitem>
+ </varlistentry>
<varlistentry>
<term><parameter>ECPGt_EORT</></term>
<listitem>
- <para>
- An <type>enum</> telling that there are no more variables.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
-
- <para>
- In the default mode, queries are committed only when <command>exec
- sql commit</command> is issued. <application>Ecpg</application>
- also supports auto-commit of transactions via the
- <option>-t</option> command-line option or via the <literal>exec
- sql set autocommit to on</literal> statement. In
- <literal>autocommit</literal> mode, each query is automatically
- committed unless it is inside an explicit transaction block. This
- mode can be explicitly turned off using <literal>exec sql set
- autocommit to off</literal>.
- </para>
- </sect2>
- </sect1>
- </chapter>
+ <para>
+ An <type>enum</> telling that there are no more variables.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </para>
+ </sect2>
+ </sect1>
+</chapter>
<!-- Keep this comment at the end of the file
Local variables:
<!--
-$Header: /cvsroot/pgsql/doc/src/sgml/ref/ecpg-ref.sgml,v 1.20 2002/07/28 15:22:20 petere Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/ref/ecpg-ref.sgml,v 1.21 2002/10/21 18:04:05 petere Exp $
PostgreSQL documentation
-->
<refentry id="APP-ECPG">
<refmeta>
- <refentrytitle
id="app-ecpg-title"><application>ecpg</application></refentrytitle>
+ <refentrytitle><application>ecpg</application></refentrytitle>
<manvolnum>1</manvolnum>
<refmiscinfo>Application</refmiscinfo>
</refmeta>
<refnamediv>
- <refname>
- <application>ecpg</application>
- </refname>
- <refpurpose>
- embedded SQL C preprocessor
- </refpurpose>
+ <refname><application>ecpg</application></refname>
+ <refpurpose>embedded SQL C preprocessor</refpurpose>
</refnamediv>
<refsynopsisdiv>
- <refsynopsisdivinfo>
- <date>1999-07-20</date>
- </refsynopsisdivinfo>
<cmdsynopsis>
<command>ecpg</command>
- <arg choice="opt">-v</arg>
- <arg choice="opt">-t</arg>
- <arg choice="opt">-I <replaceable>include-path</replaceable></arg>
- <arg choice="opt">-o <replaceable>outfile</replaceable></arg>
+ <arg choice="opt" rep="repeat"><replaceable>option</replaceable></arg>
<arg choice="plain" rep="repeat"><replaceable>file</replaceable></arg>
</cmdsynopsis>
</refsynopsisdiv>
+
<refsect1 id="APP-ECPG-description">
<title>Description</title>
<para>
- <application>ecpg</application>
- is an embedded SQL preprocessor for the C language and the
- <productname>PostgreSQL</productname>. It
- enables development of C programs with embedded SQL code.
+ <command>ecpg</command> is the embedded SQL preprocessor for C
+ programs. It converts C programs with embedded SQL statements to
+ normal C code by replacing the SQL invocations with special
+ function calls. The output files can then be processed with any C
+ compiler tool chain.
</para>
<para>
- Linus Tolke (<email>linus@epact.se</email>) was the
- original author of <application>ecpg</application> (up to version 0.2).
- Michael Meskes (<email>meskes@debian.org</email>)
- is the current author and maintainer of <application>ecpg</application>.
- Thomas Good (<email>tomg@q8.nrnet.org</email>)
- is the author of the last revision of the <application>ecpg</application> man page, on which
- this document is based.
+ <command>ecpg</command> will convert each input file given on the
+ command line to the corresponding C output file. Input files
+ preferrably have the extension <filename>.pgc</filename>, in which
+ case the extension will be replaced by <filename>.c</filename> to
+ determine the output file name. If the extension of the input file
+ is not <filename>.pgc</filename>, then the output file name is
+ computed by appending <literal>.c</literal> to the full file name.
+ The output file name can also be overridden using the
+ <option>-o</option> option.
</para>
- </refsect1>
-
-
- <refsect1>
- <title>Options</title>
-
- <para>
- <application>ecpg</application> accepts the following command
- line arguments:
- <variablelist>
- <varlistentry>
- <term>-v</term>
- <listitem>
- <para>
- Print version information.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>-t</term>
- <listitem>
- <para>
- Turn on auto-commit of transactions. In this mode, each query is
- automatically committed unless it is inside an explicit
- transaction block. In the default mode, queries are committed
- only when <command>exec sql commit</command> is issued.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>-I <replaceable class="parameter">include-path</replaceable></term>
- <listitem>
- <para>
- Specify an additional include path.
- Defaults are <filename>.</filename> (current directory),
- <filename>/usr/local/include</filename>, the
- <productname>PostgreSQL</productname> include path which is
- defined at compile time (default:
- <filename>/usr/local/pgsql/include</filename>), and
- <filename>/usr/include</filename>.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term>-o <replaceable>outfile</replaceable></term>
- <listitem>
- <para>
- Specifies that <application>ecpg</application> should write all its output to <replaceable>outfile</replaceable>.
- If no such option is given the output is written to
- <filename><replaceable>name</replaceable>.c</filename>,
- assuming the input file was
- named <filename><replaceable>name</replaceable>.pgc</filename>.
- If the input file does have the expected
- <literal>.pgc</literal> suffix, then the output file will have
- <literal>.pgc</literal> appended to the input file name.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><replaceable class="parameter">file</replaceable></term>
- <listitem>
- <para>
- The files to be processed.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </para>
+ <para>
+ This reference page does not describe the embedded SQL language.
+ See &cite-programmer; for that.
+ </para>
</refsect1>
<refsect1>
- <title>Exit Status</title>
+ <title>Options</title>
<para>
- <application>ecpg</application> returns 0 to the shell on
- successful completion, non-zero for errors.
+ <command>ecpg</command> accepts the following command-line
+ arguments:
+
+ <variablelist>
+ <varlistentry>
+ <term><option>-c</option></term>
+ <listitem>
+ <para>
+ Automatically generate C code from SQL code. Currently, this
+ works for <literal>EXEC SQL TYPE</literal>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>-D <replaceable>symbol</replaceable></option></term>
+ <listitem>
+ <para>
+ Define a C preprocessor symbol.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>-I <replaceable class="parameter">directory</replaceable></option></term>
+ <listitem>
+ <para>
+ Specify an additional include path, used to find files included
+ via <literal>EXEC SQL INCLUDE</literal>. Defaults are
+ <filename>.</filename> (current directory),
+ <filename>/usr/local/include</filename>, the
+ <productname>PostgreSQL</productname> include directory which
+ is defined at compile time (default:
+ <filename>/usr/local/pgsql/include</filename>), and
+ <filename>/usr/include</filename>, in that order.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>-o <replaceable>filename</replaceable></option></term>
+ <listitem>
+ <para>
+ Specifies that <application>ecpg</application> should write all
+ its output to the given <replaceable>filename</replaceable>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>-t</option></term>
+ <listitem>
+ <para>
+ Turn on autocommit of transactions. In this mode, each query is
+ automatically committed unless it is inside an explicit
+ transaction block. In the default mode, queries are committed
+ only when <command>EXEC SQL COMMIT</command> is issued.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>-v</option></term>
+ <listitem>
+ <para>
+ Print additional information including the version and the
+ include path.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>---help</option></term>
+ <listitem>
+ <para>
+ Show a brief summary of the command usage, then exit.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>--version</option></term>
+ <listitem>
+ <para>
+ Output version information, then exit.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
</para>
</refsect1>
<refsect1>
- <title>Usage</title>
-
- <refsect2 id="APP-ECPG-preprocessing">
- <title>Preprocessing for Compilation</title>
-
- <para>
- An embedded SQL source file must be preprocessed before
- compilation:
-<synopsis>
-ecpg [ -d ] [ -o <replaceable>file</replaceable> ] <replaceable>file</replaceable>.pgc
-</synopsis>
-
- where the optional <option>-d</option> flag turns on debugging.
- The <literal>.pgc</literal> extension is an
- arbitrary means of denoting <application>ecpg</application> source.
- </para>
-
- <para>
- You may want to redirect the preprocessor output to a log file.
- </para>
- </refsect2>
+ <title>Notes</title>
- <refsect2 id="APP-ECPG-compiling">
- <title>Compiling and Linking</title>
+ <para>
+ When compiling the preprocessed C code files, the compiler needs to
+ be able to find the <application>ECPG</> header files in the
+ PostgreSQL include directory. Therefore, one might have to use the
+ <option>-I</> option when invoking the compiler (e.g.,
+ <literal>-I/usr/local/pgsql/include</literal>).
+ </para>
- <para>
- Assuming the <productname>PostgreSQL</productname> binaries are in
- <filename>/usr/local/pgsql</filename>, you will need to compile
- and link your preprocessed source file:
+ <para>
+ Programs using C code with embedded SQL have to be linked against
+ the <filename>libecpg</filename> library, for example using the
+ flags <literal>-L/usr/local/pgsql/lib -lecpg</literal>.
+ </para>
-<synopsis>
-gcc -g -I /usr/local/pgsql/include [ -o <replaceable>file</replaceable> ] <replaceable>file</replaceable>.c -L /usr/local/pgsql/lib -lecpg -lpq
-</synopsis>
- </para>
- </refsect2>
+ <para>
+ The value of either of these directories that is appropriate for
+ the installation can be found out using <xref
+ linkend="app-pgconfig">.
+ </para>
</refsect1>
- <refsect1 id="APP-ECPG-grammar">
- <title>Grammar</title>
-
- <refsect2 id="APP-ECPG-library">
- <title>Libraries</title>
-
- <para>
- The preprocessor will prepend two directives to the source:
-
-<programlisting>
-#include <ecpgtype.h>
-#include <ecpglib.h>
-</programlisting>
- </para>
- </refsect2>
-
- <refsect2 id="APP-ecpg-declaration">
- <title>Variable Declaration</title>
-
- <para>
- Variables declared within <application>ecpg</application> source code must be prepended with:
-
-<programlisting>
-EXEC SQL BEGIN DECLARE SECTION;
-</programlisting>
- </para>
-
- <para>
- Similarly, variable declaration sections must terminate with:
-
-<programlisting>
-EXEC SQL END DECLARE SECTION;
-</programlisting>
-
- <note>
- <para>
- Prior to version 2.1.0, each variable had to be declared
- on a separate line. As of version 2.1.0 multiple variables may
- be declared on a single line:
-<programlisting>
-char foo[16], bar[16];
-</programlisting>
- </para>
- </note>
- </para>
- </refsect2>
-
- <refsect2 id="APP-ECPG-errors">
- <title>Error Handling</title>
-
- <para>
- The SQL communication area is defined with:
-
-<programlisting>
-EXEC SQL INCLUDE sqlca;
-</programlisting>
- </para>
-
- <note>
- <para>
- The <literal>sqlca</literal> is in lowercase.
- While SQL convention may be
- followed, i.e., using uppercase to separate embedded SQL
- from C statements, <literal>sqlca</literal> (which includes the <filename>sqlca.h</>
- header file) <emphasis>must</> be lowercase. This is because the
- EXEC SQL prefix indicates that this inclusion will be parsed by
- <application>ecpg</application>.
- <application>ecpg</application> observes case sensitivity
- (<filename>SQLCA.h</> will not be found).
- <command>EXEC SQL INCLUDE</command>
- can be used to include other header files
- as long as case sensitivity is observed.
- </para>
- </note>
-
- <para>
- The <literal>sqlprint</literal> command is used with the <literal>EXEC SQL WHENEVER</literal>
- statement to turn on error handling throughout the
- program:
-<programlisting>
-EXEC SQL WHENEVER sqlerror sqlprint;
-</programlisting>
-
- and
-
-<programlisting>
-EXEC SQL WHENEVER not found sqlprint;
-</programlisting>
- </para>
-
- <note>
- <para>
- This is <emphasis>not</emphasis> an exhaustive example of usage for
- the <command>EXEC SQL WHENEVER</command> statement.
- Further examples of usage may
- be found in SQL manuals (e.g., <citetitle>The LAN TIMES Guide to SQL</> by
- Groff and Weinberg).
- </para>
- </note>
- </refsect2>
-
- <refsect2 id="APP-ECPG-connecting">
- <title>Connecting to the Database Server</title>
-
- <para>
- One connects to a database using the following:
-
-<programlisting>
-EXEC SQL CONNECT TO <replaceable>dbname</replaceable>;
-</programlisting>
-
- where the database name is not quoted. Prior to version 2.1.0, the
- database name was required to be inside single quotes.
- </para>
-
- <para>
- Specifying a server and port name in the connect statement is also
- possible. The syntax is:
-
-<synopsis>
-<replaceable>dbname</replaceable>[@<replaceable>server</replaceable>][:<replaceable>port</replaceable>]
-</synopsis>
-
- or
-
-<synopsis>
-<tcp|unix>:postgresql://<replaceable>server</replaceable>[:<replaceable>port</replaceable>][/<replaceable>dbname</replaceable>][?<replaceable>options</replaceable>]
-</synopsis>
- </para>
- </refsect2>
-
- <refsect2 id="APP-ECPG-queries">
- <title>Queries</title>
-
- <para>
- In general, SQL queries acceptable to other applications such as
- <application>psql</application> can be embedded into your C
- code. Here are some examples of how to do that.
- </para>
-
- <para>
- Create Table:
-
-<programlisting>
-EXEC SQL CREATE TABLE foo (number int4, ascii char(16));
-EXEC SQL CREATE UNIQUE index num1 on foo(number);
-EXEC SQL COMMIT;
-</programlisting>
- </para>
-
- <para>
- Insert:
-
-<programlisting>
-EXEC SQL INSERT INTO foo (number, ascii) VALUES (9999, 'doodad');
-EXEC SQL COMMIT;
-</programlisting>
- </para>
-
- <para>
- Delete:
-
-<programlisting>
-EXEC SQL DELETE FROM foo WHERE number = 9999;
-EXEC SQL COMMIT;
-</programlisting>
- </para>
-
- <para>
- Singleton Select:
-
-<programlisting>
-EXEC SQL SELECT foo INTO :FooBar FROM table1 WHERE ascii = 'doodad';
-</programlisting>
- </para>
-
- <para>
- Select using Cursors:
-
-<programlisting>
-EXEC SQL DECLARE foo_bar CURSOR FOR
- SELECT number, ascii FROM foo
- ORDER BY ascii;
-EXEC SQL FETCH foo_bar INTO :FooBar, DooDad;
-...
-EXEC SQL CLOSE foo_bar;
-EXEC SQL COMMIT;
-</programlisting>
- </para>
+ <refsect1>
+ <title>Examples</title>
- <para>
- Updates:
+ <para>
+ If you have an embedded SQL C source file named
+ <filename>prog1.pgc</filename>, you can create an executable
+ program using the following sequence of commands:
<programlisting>
-EXEC SQL UPDATE foo
- SET ascii = 'foobar'
- WHERE number = 9999;
-EXEC SQL COMMIT;
+ecpg prog1.pgc
+cc -I/usr/local/pgsql/include -c prog1.c
+cc -o prog1 prog1.o -L/usr/local/pgsql/lib -lecpg
</programlisting>
- </para>
- </refsect2>
- </refsect1>
-
- <refsect1 id="APP-ECPG-notes">
- <title>Notes</title>
- <para>
- The complete structure definition MUST be listed
- inside the declare section.
- </para>
-
- <para>
- See the <filename>TODO</filename> file in the source for some more
- missing features.
</para>
-
</refsect1>
<para>
<citetitle>PostgreSQL Programmer's Guide</citetitle> for a more
- detailed description of the embedded SQL interface.
+ detailed description of the embedded SQL interface
</para>
</refsect1>
projects / postgresql / commitdiff