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+$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_table.sgml,v 1.24 2000/04/14 22:13:24 momjian Exp $
Postgres documentation
-->
<term>MATCH <replaceable class="parameter">matchtype</replaceable></term>
<listitem>
<para>
- The type of comparison to do between the table data. There are
- three types of matching, MATCH FULL, MATCH PARTIAL, and the
- unspecified match type used if no match type is specified.
- MATCH PARTIAL is not
- currently supported.
+ There are three match types: MATCH FULL, MATCH PARTIAL, and a
+ default match type if none is specified. MATCH FULL will not
+ allow one column of a multi-column foreign key to be NULL
+ unless all foreign key columns are NULL. The default MATCH type
+ allows a single foreign key column to be NULL while other parts
+ of the foreign key are not NULL. MATCH PARTIAL is not currently
+ supported.
</para>
</listitem>
</varlistentry>
</title>
<para>
Currently <productname>Postgres</productname> only supports MATCH
- FULL and an unspecified match type. In addition, the referenced
+ FULL and a default match type. In addition, the referenced
columns are supposed to be the columns of a UNIQUE constraint in
the referenced table, however <productname>Postgres</productname>
does not enforce this.
<term>MATCH <replaceable class="parameter">matchtype</replaceable></term>
<listitem>
<para>
- The type of comparison to do between the table data. There are
- three types of matching, MATCH FULL, MATCH PARTIAL, and the
- unspecified match type used if no match type is specified.
- MATCH PARTIAL is not currently supported.
+ There are three match types: MATCH FULL, MATCH PARTIAL, and a
+ default match type if none is specified. MATCH FULL will not
+ allow one column of a multi-column foreign key to be NULL
+ unless all foreign key columns are NULL. The default MATCH type
+ allows a single foreign key column to be NULL while other parts
+ of the foreign key are not NULL. MATCH PARTIAL is not currently
+ supported.
</para>
</listitem>
</varlistentry>