<!--
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> [ * ]
    [ FOR PORTION OF <replaceable class="parameter">range_column_name</replaceable> <replaceable class="parameter">for_portion_of_target</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 [ WITH ( { OLD | NEW } AS <replaceable class="parameter">output_alias</replaceable> [, ...] ) ]
                { * | <replaceable class="parameter">output_expression</replaceable> [ [ AS ] <replaceable class="parameter">output_name</replaceable> ] } [, ...] ]

<phrase>where <replaceable class="parameter">for_portion_of_target</replaceable> is:</phrase>

{ FROM <replaceable class="parameter">start_time</replaceable> TO <replaceable class="parameter">end_time</replaceable> |
  ( <replaceable class="parameter">portion</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>
   If the <literal>FOR PORTION OF</literal> clause is used, the delete will
   only affect rows that overlap the given portion.  Furthermore, if a row's
   application time extends outside the <literal>FOR PORTION OF</literal>
   bounds, then the delete will only change the application time within those
   bounds.  In effect, only the history targeted by <literal>FOR PORTION
   OF</literal> is deleted, and no moments outside.  Furthermore, after a row
   is deleted, new <glossterm linkend="glossary-temporal-leftovers">temporal
   leftovers</glossterm> might be inserted: rows whose range or multirange
   receives the remaining application time outside the targeted bounds, with
   the original values in their other columns. For range columns, there will
   be zero to two inserted records, depending on whether the original
   application time was completely deleted, extended before/after the change,
   or both.  Multiranges never require two temporal leftovers, because one
   value can always contain whatever application time remains.
  </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>.
   When <literal>FOR PORTION OF</literal> is used, the secondary inserts do
   not require <literal>INSERT</literal> privilege on the table.  (This is
   because conceptually no new information is being added; the inserted rows
   only preserve existing data about the untargeted time period.)  Row-level
   security INSERT policies are still checked for these leftover inserts.
  </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">range_column_name</replaceable></term>
    <listitem>
     <para>
      The range or multirange column to use when performing a temporal delete.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">for_portion_of_target</replaceable></term>
    <listitem>
     <para>
      The portion to delete. If targeting a range column, this can be in the
      form <literal>FROM</literal> <replaceable
      class="parameter">start_time</replaceable> <literal>TO</literal>
      <replaceable class="parameter">end_time</replaceable>.  Otherwise, it
      must be in the form <literal>(</literal><replaceable
      class="parameter">portion</replaceable><literal>)</literal>, where
      <replaceable class="parameter">portion</replaceable> is an expression
      that yields a value of the same type as <replaceable
      class="parameter">range_column_name</replaceable>.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">start_time</replaceable></term>
    <listitem>
     <para>
      The earliest time (inclusive) to change in a temporal delete.  This must
      be a value matching the base type of the range from <replaceable
      class="parameter">range_column_name</replaceable>.  A null value here
      indicates a delete whose beginning is unbounded (as with range types).
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">end_time</replaceable></term>
    <listitem>
     <para>
      The latest time (exclusive) to change in a temporal delete.  This must
      be a value matching the base type of the range from <replaceable
      class="parameter">range_column_name</replaceable>.  A null value here
      indicates a delete whose end is unbounded (as with range types).
     </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 or <literal>FOR PORTION
      OF</literal>.  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_alias</replaceable></term>
    <listitem>
     <para>
      An optional substitute name for <literal>OLD</literal> or
      <literal>NEW</literal> rows in the <literal>RETURNING</literal> list.
     </para>

     <para>
      By default, old values from the target table can be returned by writing
      <literal>OLD.<replaceable class="parameter">column_name</replaceable></literal>
      or <literal>OLD.*</literal>, and new values can be returned by writing
      <literal>NEW.<replaceable class="parameter">column_name</replaceable></literal>
      or <literal>NEW.*</literal>.  When an alias is provided, these names are
      hidden and the old or new rows must be referred to using the alias.
      For example <literal>RETURNING WITH (OLD AS o, NEW AS n) o.*, n.*</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>

     <para>
      A column name or <literal>*</literal> may be qualified using
      <literal>OLD</literal> or <literal>NEW</literal>, or the corresponding
      <replaceable class="parameter">output_alias</replaceable> for
      <literal>OLD</literal> or <literal>NEW</literal>, to cause old or new
      values to be returned.  An unqualified column name, or
      <literal>*</literal>, or a column name or <literal>*</literal> qualified
      using the target table name or alias will return old values.
     </para>

     <para>
      For a simple <command>DELETE</command>, all new values will be
      <literal>NULL</literal>.  However, if an <literal>ON DELETE</literal>
      rule causes an <command>INSERT</command> or <command>UPDATE</command>
      to be executed instead, the new values may be non-<literal>NULL</literal>.
     </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).
   If <literal>FOR PORTION OF</literal> was used, the
   <replaceable class="parameter">count</replaceable> does not include
   <glossterm linkend="glossary-temporal-leftovers">temporal leftovers</glossterm>
   that were inserted.
  </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. If <literal>FOR PORTION OF</literal> was used, the
   <literal>RETURNING</literal> clause gives one result for each deleted row,
   but does not include inserted
   <glossterm linkend="glossary-temporal-leftovers">temporal leftovers</glossterm>.
   The value of the application-time column matches the old value of the deleted
   row(s). Note this will represent more application time than was actually erased,
   if temporal leftovers were inserted.
  </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>

  <para>
   When <literal>FOR PORTION OF</literal> is used, this can result in users
   who don't have <literal>INSERT</literal> privileges firing
   <literal>INSERT</literal> triggers.  This should be considered when
   using <literal>SECURITY DEFINER</literal> trigger functions.
  </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 <structname>films</structname>:
<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>

  <para>
   An example of a temporal delete:
<programlisting>
DELETE FROM products
  FOR PORTION OF valid_at FROM '2021-08-01' TO '2023-09-01'
  WHERE product_no = 5;
</programlisting>
  </para>

  <para>
   While there is no <literal>LIMIT</literal> clause
   for <command>DELETE</command>, it is possible to get a similar effect
   using the same method described in <link linkend="update-limit">the
   documentation of <command>UPDATE</command></link>:
<programlisting>
WITH delete_batch AS (
  SELECT l.ctid FROM user_logs AS l
    WHERE l.status = 'archived'
    ORDER BY l.creation_date
    FOR UPDATE
    LIMIT 10000
)
DELETE FROM user_logs AS dl
  USING delete_batch AS del
  WHERE dl.ctid = del.ctid;
</programlisting>
   This use of <structfield>ctid</structfield> is only safe because
   the query is repeatedly run, avoiding the problem of changed
   <structfield>ctid</structfield>s.
  </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>
