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><H1
><A
NAME="SQL-DELETE"
></A
>DELETE</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN55745"
></A
><H2
>Name</H2
>DELETE -- delete rows of a table</DIV
><A
NAME="AEN55748"
></A
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN55750"
></A
><H2
>Synopsis</H2
><PRE
CLASS="SYNOPSIS"
>DELETE FROM [ ONLY ] <TT
CLASS="REPLACEABLE"
><I
>table</I
></TT
> [ [ AS ] <TT
CLASS="REPLACEABLE"
><I
>alias</I
></TT
> ]
[ USING <TT
CLASS="REPLACEABLE"
><I
>usinglist</I
></TT
> ]
[ WHERE <TT
CLASS="REPLACEABLE"
><I
>condition</I
></TT
> | WHERE CURRENT OF <TT
CLASS="REPLACEABLE"
><I
>cursor_name</I
></TT
> ]
[ RETURNING * | <TT
CLASS="REPLACEABLE"
><I
>output_expression</I
></TT
> [ AS <TT
CLASS="REPLACEABLE"
><I
>output_name</I
></TT
> ] [, ...] ]</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN55759"
></A
><H2
>Description</H2
><P
> <TT
CLASS="COMMAND"
>DELETE</TT
> deletes rows that satisfy the
<TT
CLASS="LITERAL"
>WHERE</TT
> clause from the specified table. If the
<TT
CLASS="LITERAL"
>WHERE</TT
> clause is absent, the effect is to delete
all rows in the table. The result is a valid, but empty table.
</P
><DIV
CLASS="TIP"
><BLOCKQUOTE
CLASS="TIP"
><P
><B
>Tip: </B
> <A
HREF="sql-truncate.html"
><I
>TRUNCATE</I
></A
> is a
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> extension that provides a
faster mechanism to remove all rows from a table.
</P
></BLOCKQUOTE
></DIV
><P
> By default, <TT
CLASS="COMMAND"
>DELETE</TT
> will delete rows in the
specified table and all its child tables. If you wish to delete only
from the specific table mentioned, you must use the
<TT
CLASS="LITERAL"
>ONLY</TT
> clause.
</P
><P
> 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 <TT
CLASS="LITERAL"
>USING</TT
> clause.
Which technique is more appropriate depends on the specific
circumstances.
</P
><P
> The optional <TT
CLASS="LITERAL"
>RETURNING</TT
> clause causes <TT
CLASS="COMMAND"
>DELETE</TT
>
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 <TT
CLASS="LITERAL"
>USING</TT
>, can be computed.
The syntax of the <TT
CLASS="LITERAL"
>RETURNING</TT
> list is identical to that of the
output list of <TT
CLASS="COMMAND"
>SELECT</TT
>.
</P
><P
> You must have the <TT
CLASS="LITERAL"
>DELETE</TT
> privilege on the table
to delete from it, as well as the <TT
CLASS="LITERAL"
>SELECT</TT
>
privilege for any table in the <TT
CLASS="LITERAL"
>USING</TT
> clause or
whose values are read in the <TT
CLASS="REPLACEABLE"
><I
>condition</I
></TT
>.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN55785"
></A
><H2
>Parameters</H2
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="LITERAL"
>ONLY</TT
></DT
><DD
><P
> If specified, delete rows from the named table only. When not
specified, any tables inheriting from the named table are also processed.
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>table</I
></TT
></DT
><DD
><P
> The name (optionally schema-qualified) of an existing table.
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>alias</I
></TT
></DT
><DD
><P
> A substitute name for the target table. When an alias is
provided, it completely hides the actual name of the table. For
example, given <TT
CLASS="LITERAL"
>DELETE FROM foo AS f</TT
>, the remainder
of the <TT
CLASS="COMMAND"
>DELETE</TT
> statement must refer to this
table as <TT
CLASS="LITERAL"
>f</TT
> not <TT
CLASS="LITERAL"
>foo</TT
>.
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>usinglist</I
></TT
></DT
><DD
><P
> A list of table expressions, allowing columns from other tables
to appear in the <TT
CLASS="LITERAL"
>WHERE</TT
> condition. This is similar
to the list of tables that can be specified in the <A
HREF="sql-select.html#SQL-FROM"
><I
><I
>FROM</I
> Clause</I
></A
> of a
<TT
CLASS="COMMAND"
>SELECT</TT
> statement; for example, an alias for
the table name can be specified. Do not repeat the target table
in the <TT
CLASS="REPLACEABLE"
><I
>usinglist</I
></TT
>,
unless you wish to set up a self-join.
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>condition</I
></TT
></DT
><DD
><P
> An expression that returns a value of type <TT
CLASS="TYPE"
>boolean</TT
>.
Only rows for which this expression returns <TT
CLASS="LITERAL"
>true</TT
>
will be deleted.
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>cursor_name</I
></TT
></DT
><DD
><P
> The name of the cursor to use in a <TT
CLASS="LITERAL"
>WHERE CURRENT OF</TT
>
condition. The row to be deleted is the one most recently fetched
from this cursor. The cursor must be a simple (non-join, non-aggregate)
query on the <TT
CLASS="COMMAND"
>DELETE</TT
>'s target table.
Note that <TT
CLASS="LITERAL"
>WHERE CURRENT OF</TT
> cannot be
specified together with a Boolean condition.
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>output_expression</I
></TT
></DT
><DD
><P
> An expression to be computed and returned by the <TT
CLASS="COMMAND"
>DELETE</TT
>
command after each row is deleted. The expression can use any
column names of the <TT
CLASS="REPLACEABLE"
><I
>table</I
></TT
>
or table(s) listed in <TT
CLASS="LITERAL"
>USING</TT
>.
Write <TT
CLASS="LITERAL"
>*</TT
> to return all columns.
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>output_name</I
></TT
></DT
><DD
><P
> A name to use for a returned column.
</P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN55845"
></A
><H2
>Outputs</H2
><P
> On successful completion, a <TT
CLASS="COMMAND"
>DELETE</TT
> command returns a command
tag of the form
</P><PRE
CLASS="SCREEN"
>DELETE <TT
CLASS="REPLACEABLE"
><I
>count</I
></TT
></PRE
><P>
The <TT
CLASS="REPLACEABLE"
><I
>count</I
></TT
> is the number
of rows deleted. If <TT
CLASS="REPLACEABLE"
><I
>count</I
></TT
> is
0, no rows matched the <TT
CLASS="REPLACEABLE"
><I
>condition</I
></TT
> (this is not considered
an error).
</P
><P
> If the <TT
CLASS="COMMAND"
>DELETE</TT
> command contains a <TT
CLASS="LITERAL"
>RETURNING</TT
>
clause, the result will be similar to that of a <TT
CLASS="COMMAND"
>SELECT</TT
>
statement containing the columns and values defined in the
<TT
CLASS="LITERAL"
>RETURNING</TT
> list, computed over the row(s) deleted by the
command.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN55859"
></A
><H2
>Notes</H2
><P
> <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> lets you reference columns of
other tables in the <TT
CLASS="LITERAL"
>WHERE</TT
> condition by specifying the
other tables in the <TT
CLASS="LITERAL"
>USING</TT
> clause. For example,
to delete all films produced by a given producer, one can do:
</P><PRE
CLASS="PROGRAMLISTING"
>DELETE FROM films USING producers
WHERE producer_id = producers.id AND producers.name = 'foo';</PRE
><P>
What is essentially happening here is a join between <TT
CLASS="STRUCTNAME"
>films</TT
>
and <TT
CLASS="STRUCTNAME"
>producers</TT
>, with all successfully joined
<TT
CLASS="STRUCTNAME"
>films</TT
> rows being marked for deletion.
This syntax is not standard. A more standard way to do it is:
</P><PRE
CLASS="PROGRAMLISTING"
>DELETE FROM films
WHERE producer_id IN (SELECT id FROM producers WHERE name = 'foo');</PRE
><P>
In some cases the join style is easier to write or faster to
execute than the sub-select style.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN55870"
></A
><H2
>Examples</H2
><P
> Delete all films but musicals:
</P><PRE
CLASS="PROGRAMLISTING"
>DELETE FROM films WHERE kind <> 'Musical';</PRE
><P>
</P
><P
> Clear the table <TT
CLASS="LITERAL"
>films</TT
>:
</P><PRE
CLASS="PROGRAMLISTING"
>DELETE FROM films;</PRE
><P>
</P
><P
> Delete completed tasks, returning full details of the deleted rows:
</P><PRE
CLASS="PROGRAMLISTING"
>DELETE FROM tasks WHERE status = 'DONE' RETURNING *;</PRE
><P>
</P
><P
> Delete the row of <TT
CLASS="STRUCTNAME"
>tasks</TT
> on which the cursor
<TT
CLASS="LITERAL"
>c_tasks</TT
> is currently positioned:
</P><PRE
CLASS="PROGRAMLISTING"
>DELETE FROM tasks WHERE CURRENT OF c_tasks;</PRE
><P>
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN55883"
></A
><H2
>Compatibility</H2
><P
> This command conforms to the <ACRONYM
CLASS="ACRONYM"
>SQL</ACRONYM
> standard, except
that the <TT
CLASS="LITERAL"
>USING</TT
> and <TT
CLASS="LITERAL"
>RETURNING</TT
> clauses
are <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> extensions.
</P
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>
distrib
>
Mandriva
>
2008.1
>
x86_64
>
media
>
main-testing
>
by-pkgid
>
bab02a23fa9f3df8d66a9a3231b50245
>
files
>
759
