Adding upstream version 16.2.upstream/16.2

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 289 insertions, 0 deletions

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+<!--
+doc/src/sgml/ref/delete.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="sql-delete">
+ <indexterm zone="sql-delete">
+  <primary>DELETE</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>DELETE</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>DELETE</refname>
+  <refpurpose>delete rows of a table</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+[ WITH [ RECURSIVE ] <replaceable class="parameter">with_query</replaceable> [, ...] ]
+DELETE FROM [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [ [ AS ] <replaceable class="parameter">alias</replaceable> ]
+    [ USING <replaceable class="parameter">from_item</replaceable> [, ...] ]
+    [ WHERE <replaceable class="parameter">condition</replaceable> | WHERE CURRENT OF <replaceable class="parameter">cursor_name</replaceable> ]
+    [ RETURNING * | <replaceable class="parameter">output_expression</replaceable> [ [ AS ] <replaceable class="parameter">output_name</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>
+     <link linkend="sql-truncate"><command>TRUNCATE</command></link> provides a
+     faster mechanism to remove all rows from a table.
+    </para>
+   </tip>
+
+  <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>
+   The optional <literal>RETURNING</literal> clause causes <command>DELETE</command>
+   to compute and return value(s) based on each row actually deleted.
+   Any expression using the table's columns, and/or columns of other
+   tables mentioned in <literal>USING</literal>, can be computed.
+   The syntax of the <literal>RETURNING</literal> list is identical to that of the
+   output list of <command>SELECT</command>.
+  </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 in the <literal>USING</literal> clause or
+   whose values are read in the <replaceable
+   class="parameter">condition</replaceable>.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+  <variablelist>
+   <varlistentry>
+    <term><replaceable class="parameter">with_query</replaceable></term>
+    <listitem>
+     <para>
+      The <literal>WITH</literal> clause allows you to specify one or more
+      subqueries that can be referenced by name in the <command>DELETE</command>
+      query. See <xref linkend="queries-with"/> and <xref linkend="sql-select"/>
+      for details.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">table_name</replaceable></term>
+    <listitem>
+     <para>
+      The name (optionally schema-qualified) of the table to delete rows
+      from.  If <literal>ONLY</literal> is specified before the table name,
+      matching rows are deleted from the named table only.  If
+      <literal>ONLY</literal> is not specified, matching rows are also deleted
+      from any tables inheriting from the named table.  Optionally,
+      <literal>*</literal> can be specified after the table name to explicitly
+      indicate that descendant tables are included.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">alias</replaceable></term>
+    <listitem>
+     <para>
+      A substitute name for the target table. When an alias is
+      provided, it completely hides the actual name of the table.  For
+      example, given <literal>DELETE FROM foo AS f</literal>, the remainder
+      of the <command>DELETE</command> statement must refer to this
+      table as <literal>f</literal> not <literal>foo</literal>.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">from_item</replaceable></term>
+    <listitem>
+     <para>
+      A table expression allowing columns from other tables to appear
+      in the <literal>WHERE</literal> condition.  This uses the same
+      syntax as the <link linkend="sql-from"><literal>FROM</literal></link>
+      clause of a <command>SELECT</command> statement; for example, an alias
+      for the table name can be specified.  Do not repeat the target
+      table as a <replaceable class="parameter">from_item</replaceable>
+      unless you wish to set up a self-join (in which case it must appear
+      with an alias in the <replaceable>from_item</replaceable>).
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">condition</replaceable></term>
+    <listitem>
+     <para>
+      An expression that returns a value of type <type>boolean</type>.
+      Only rows for which this expression returns <literal>true</literal>
+      will be deleted.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">cursor_name</replaceable></term>
+    <listitem>
+     <para>
+      The name of the cursor to use in a <literal>WHERE CURRENT OF</literal>
+      condition.  The row to be deleted is the one most recently fetched
+      from this cursor.  The cursor must be a non-grouping
+      query on the <command>DELETE</command>'s target table.
+      Note that <literal>WHERE CURRENT OF</literal> cannot be
+      specified together with a Boolean condition.  See
+      <xref linkend="sql-declare"/>
+      for more information about using cursors with
+      <literal>WHERE CURRENT OF</literal>.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">output_expression</replaceable></term>
+    <listitem>
+     <para>
+      An expression to be computed and returned by the <command>DELETE</command>
+      command after each row is deleted.  The expression can use any
+      column names of the table named by <replaceable class="parameter">table_name</replaceable>
+      or table(s) listed in <literal>USING</literal>.
+      Write <literal>*</literal> to return all columns.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">output_name</replaceable></term>
+    <listitem>
+     <para>
+      A name to use for a returned column.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+ </refsect1>
+
+ <refsect1>
+  <title>Outputs</title>
+
+  <para>
+   On successful completion, a <command>DELETE</command> 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.  Note that the number may be less than the number of
+   rows that matched the <replaceable
+   class="parameter">condition</replaceable> when deletes were
+   suppressed by a <literal>BEFORE DELETE</literal> trigger.  If <replaceable
+   class="parameter">count</replaceable> is 0, no rows were deleted by
+   the query (this is not considered an error).
+  </para>
+
+  <para>
+   If the <command>DELETE</command> command contains a <literal>RETURNING</literal>
+   clause, the result will be similar to that of a <command>SELECT</command>
+   statement containing the columns and values defined in the
+   <literal>RETURNING</literal> list, computed over the row(s) deleted by the
+   command.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Notes</title>
+
+  <para>
+   <productname>PostgreSQL</productname> lets you reference columns of
+   other tables in the <literal>WHERE</literal> condition by specifying the
+   other tables in the <literal>USING</literal> clause.  For example,
+   to delete all films produced by a given producer, one can do:
+<programlisting>
+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</structname>
+   and <structname>producers</structname>, with all successfully joined
+   <structname>films</structname> 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.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Examples</title>
+
+  <para>
+   Delete all films but musicals:
+<programlisting>
+DELETE FROM films WHERE kind &lt;&gt; 'Musical';
+</programlisting>
+  </para>
+
+  <para>
+   Clear the table <literal>films</literal>:
+<programlisting>
+DELETE FROM films;
+</programlisting>
+  </para>
+
+  <para>
+   Delete completed tasks, returning full details of the deleted rows:
+<programlisting>
+DELETE FROM tasks WHERE status = 'DONE' RETURNING *;
+</programlisting>
+  </para>
+
+   <para>
+   Delete the row of <structname>tasks</structname> on which the cursor
+   <literal>c_tasks</literal> is currently positioned:
+<programlisting>
+DELETE FROM tasks WHERE CURRENT OF c_tasks;
+</programlisting></para>
+ </refsect1>
+
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   This command conforms to the <acronym>SQL</acronym> standard, except
+   that the <literal>USING</literal> and <literal>RETURNING</literal> clauses
+   are <productname>PostgreSQL</productname> extensions, as is the ability
+   to use <literal>WITH</literal> with <command>DELETE</command>.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-truncate"/></member>
+  </simplelist>
+ </refsect1>
+</refentry>