From 92c001bbaf86ac171fb361e81aa962ae873b52c2 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Fri, 17 Dec 2004 04:50:32 +0000 Subject: [PATCH] Minor copy-editing in tutorial. --- doc/src/sgml/advanced.sgml | 4 ++-- doc/src/sgml/query.sgml | 26 +++++++++++++------------- doc/src/sgml/start.sgml | 4 ++-- 3 files changed, 17 insertions(+), 17 deletions(-) diff --git a/doc/src/sgml/advanced.sgml b/doc/src/sgml/advanced.sgml index 64ff4616e2..82d9e229b3 100644 --- a/doc/src/sgml/advanced.sgml +++ b/doc/src/sgml/advanced.sgml @@ -1,5 +1,5 @@ @@ -196,7 +196,7 @@ UPDATE branches SET balance = balance + 100.00 and won't be lost even if a crash ensues shortly thereafter. For example, if we are recording a cash withdrawal by Bob, we do not want any chance that the debit to his account will - disappear in a crash just as he walks out the bank door. + disappear in a crash just after he walks out the bank door. A transactional database guarantees that all the updates made by a transaction are logged in permanent storage (i.e., on disk) before the transaction is reported complete. diff --git a/doc/src/sgml/query.sgml b/doc/src/sgml/query.sgml index 8240281b3d..33294afd3c 100644 --- a/doc/src/sgml/query.sgml +++ b/doc/src/sgml/query.sgml @@ -1,5 +1,5 @@ @@ -154,7 +154,7 @@ CREATE TABLE weather ( - PostgreSQL supports the usual + PostgreSQL supports the standard SQL types int, smallint, real, double precision, char(N), @@ -297,8 +297,8 @@ SELECT * FROM weather; While SELECT * is useful for off-the-cuff - queries, it is considered bad style in production code for - maintenance reasons: adding a column to the table changes the results. + queries, it is widely considered bad style in production code, + since adding a column to the table would change the results. The output should be: @@ -400,9 +400,9 @@ SELECT DISTINCT city the cities table, and select the pairs of rows where these values match. - This is only a conceptual model. The actual join may - be performed in a more efficient manner, but this is invisible - to the user. + This is only a conceptual model. The join is usually performed + in a more efficient manner than actually comparing each possible + pair of rows, but this is invisible to the user. This would be accomplished by the following query: @@ -727,15 +727,15 @@ SELECT city, max(temp_lo) aggregates are computed. Thus, the WHERE clause must not contain aggregate functions; it makes no sense to try to use an aggregate to determine which rows - will be inputs to the aggregates. On the other hand, + will be inputs to the aggregates. On the other hand, the HAVING clause always contains aggregate functions. (Strictly speaking, you are allowed to write a HAVING - clause that doesn't use aggregates, but it's wasteful: The same condition + clause that doesn't use aggregates, but it's wasteful. The same condition could be used more efficiently at the WHERE stage.) - Observe that we can apply the city name restriction in + In the previous example, we can apply the city name restriction in WHERE, since it needs no aggregate. This is more efficient than adding the restriction to HAVING, because we avoid doing the grouping and aggregate calculations @@ -788,10 +788,10 @@ SELECT * FROM weather; + Rows can be removed from a table using the DELETE + command. Suppose you are no longer interested in the weather of Hayward. - Then you can do the following to delete those rows from the table. - Deletions are performed using the DELETE - command: + Then you can do the following to delete those rows from the table: DELETE FROM weather WHERE city = 'Hayward'; diff --git a/doc/src/sgml/start.sgml b/doc/src/sgml/start.sgml index fc53a20a14..c40f76c8ce 100644 --- a/doc/src/sgml/start.sgml +++ b/doc/src/sgml/start.sgml @@ -1,5 +1,5 @@ @@ -218,7 +218,7 @@ createdb: database creation failed: ERROR: permission denied to create database operating system account. As it happens, there will always be a PostgreSQL user account that has the same name as the operating system user that started the server, - and it also happens that the user always has permission to + and it also happens that that user always has permission to create databases. Instead of logging in as that user you can also specify the option everywhere to select a PostgreSQL user name to connect as. -- 2.40.0