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<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/delete.sgml,v 1.22 2005/01/09 05:57:45 tgl Exp $
PostgreSQL documentation
-->
<refentry id="SQL-DELETE">
<refmeta>
<refentrytitle id="SQL-DELETE-TITLE">DELETE</refentrytitle>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>DELETE</refname>
<refpurpose>delete rows of a table</refpurpose>
</refnamediv>
<indexterm zone="sql-delete">
<primary>DELETE</primary>
</indexterm>
<refsynopsisdiv>
<synopsis>
DELETE FROM [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ WHERE <replaceable class="PARAMETER">condition</replaceable> ]
</synopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
<command>DELETE</command> deletes rows that satisfy the
<literal>WHERE</literal> clause from the specified table. If the
<literal>WHERE</literal> clause is absent, the effect is to delete
all rows in the table. The result is a valid, but empty table.
</para>
<tip>
<para>
<xref linkend="sql-truncate" endterm="sql-truncate-title"> is a
<productname>PostgreSQL</productname> extension that provides a
faster mechanism to remove all rows from a table.
</para>
</tip>
<para>
By default, <command>DELETE</command> will delete rows in the
specified table and all its subtables. If you wish to delete only
from the specific table mentioned, you must use the
<literal>ONLY</literal> clause.
</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
class="parameter">condition</replaceable>.
</para>
</refsect1>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term><replaceable class="parameter">table</replaceable></term>
<listitem>
<para>
The name (optionally schema-qualified) of an existing table.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">condition</replaceable></term>
<listitem>
<para>
A value expression that returns a value of type
<type>boolean</type> that determines the rows which are to be
deleted.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Outputs</title>
<para>
On successful completion, a <command>DELETE</> command returns a command
tag of the form
<screen>
DELETE <replaceable class="parameter">count</replaceable>
</screen>
The <replaceable class="parameter">count</replaceable> is the number
of rows deleted. If <replaceable class="parameter">count</replaceable> is
0, no rows matched the <replaceable
class="parameter">condition</replaceable> (this is not considered
an error).
</para>
</refsect1>
<refsect1>
<title>Notes</title>
<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
<programlisting>
DELETE FROM films
WHERE producer_id = producers.id AND producers.name = 'foo';
</programlisting>
What is essentially happening here is a join between <structname>films</>
and <structname>producers</>, with all successfully joined
<structname>films</> rows being marked for deletion.
This syntax is not standard. A more standard way to do it is
<programlisting>
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.
</para>
</refsect1>
<refsect1>
<title>Examples</title>
<para>
Delete all films but musicals:
<programlisting>
DELETE FROM films WHERE kind <> 'Musical';
</programlisting>
</para>
<para>
Clear the table <literal>films</literal>:
<programlisting>
DELETE FROM films;
</programlisting>
</para>
</refsect1>
<refsect1>
<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.
</para>
</refsect1>
</refentry>
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