diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/ref/delete.sgml | 56 |
1 files changed, 43 insertions, 13 deletions
diff --git a/doc/src/sgml/ref/delete.sgml b/doc/src/sgml/ref/delete.sgml index 6b6c8bf66d8..954391a228b 100644 --- a/doc/src/sgml/ref/delete.sgml +++ b/doc/src/sgml/ref/delete.sgml @@ -1,5 +1,5 @@ <!-- -$PostgreSQL: pgsql/doc/src/sgml/ref/delete.sgml,v 1.22 2005/01/09 05:57:45 tgl Exp $ +$PostgreSQL: pgsql/doc/src/sgml/ref/delete.sgml,v 1.23 2005/04/07 01:51:37 neilc Exp $ PostgreSQL documentation --> @@ -20,7 +20,9 @@ PostgreSQL documentation <refsynopsisdiv> <synopsis> -DELETE FROM [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ WHERE <replaceable class="PARAMETER">condition</replaceable> ] +DELETE FROM [ ONLY ] <replaceable class="PARAMETER">table</replaceable> + [ USING <replaceable class="PARAMETER">usinglist</replaceable> ] + [ WHERE <replaceable class="PARAMETER">condition</replaceable> ] </synopsis> </refsynopsisdiv> @@ -50,9 +52,18 @@ DELETE FROM [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ WHERE </para> <para> + There are two ways to delete rows in a table using information + contained in other tables in the database: using sub-selects, or + specifying additional tables in the <literal>USING</literal> clause. + Which technique is more appropriate depends on the specific + circumstances. + </para> + + <para> You must have the <literal>DELETE</literal> privilege on the table to delete from it, as well as the <literal>SELECT</literal> - privilege for any table whose values are read in the <replaceable + privilege for any table in the <literal>USING</literal> clause or + whose values are read in the <replaceable class="parameter">condition</replaceable>. </para> </refsect1> @@ -71,6 +82,20 @@ DELETE FROM [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ WHERE </varlistentry> <varlistentry> + <term><replaceable class="PARAMETER">usinglist</replaceable></term> + <listitem> + <para> + A list of table expressions, allowing columns from other tables + to appear in the <literal>WHERE</> condition. This is similar + to the list of tables that can be specified in the <xref + linkend="sql-from" endterm="sql-from-title"> of a + <command>SELECT</command> statement; for example, an alias for + the table name can be specified. + </para> + </listitem> + </varlistentry> + + <varlistentry> <term><replaceable class="parameter">condition</replaceable></term> <listitem> <para> @@ -105,10 +130,11 @@ DELETE <replaceable class="parameter">count</replaceable> <para> <productname>PostgreSQL</productname> lets you reference columns of - other tables in the <literal>WHERE</> condition. For example, to - delete all films produced by a given producer, one might do + other tables in the <literal>WHERE</> condition by specifying the + other tables in the <literal>USING</literal> clause. For example, + to delete all films produced by a given producer, one might do <programlisting> -DELETE FROM films +DELETE FROM films USING producers WHERE producer_id = producers.id AND producers.name = 'foo'; </programlisting> What is essentially happening here is a join between <structname>films</> @@ -120,10 +146,13 @@ DELETE FROM films WHERE producer_id IN (SELECT id FROM producers WHERE name = 'foo'); </programlisting> In some cases the join style is easier to write or faster to - execute than the sub-select style. One objection to the join style - is that there is no explicit list of what tables are being used, - which makes the style somewhat error-prone; also it cannot handle - self-joins. + execute than the sub-select style. + </para> + + <para> + If <varname>add_missing_from</varname> is enabled, any relations + mentioned in the <literal>WHERE</literal> condition will be + implicitly added to the <literal>USING</literal> clause. </para> </refsect1> @@ -149,9 +178,10 @@ DELETE FROM films; <title>Compatibility</title> <para> - This command conforms to the SQL standard, except that the ability to - reference other tables in the <literal>WHERE</> clause is a - <productname>PostgreSQL</productname> extension. + This command conforms to the SQL standard, except that the + <literal>USING</> clause and the ability to reference other tables + in the <literal>WHERE</> clause are <productname>PostgreSQL</> + extensions. </para> </refsect1> </refentry> |