DELETE(7)                                                 SQL Commands                                                 DELETE(7)



NAME
       DELETE - delete rows of a table


SYNOPSIS
       DELETE FROM [ ONLY ] table [ [ AS ] alias ]
           [ USING usinglist ]
           [ WHERE condition | WHERE CURRENT OF cursor_name ]
           [ RETURNING * | output_expression [ [ AS ] output_name ] [, ...] ]


DESCRIPTION
       DELETE  deletes rows that satisfy the WHERE clause from the specified table. If the WHERE clause is absent, the effect is
       to delete all rows in the table. The result is a valid, but empty table.

              Tip: TRUNCATE [truncate(7)] is a PostgreSQL extension that provides a faster mechanism to remove all rows  from  a
              table.


       By  default, DELETE 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 ONLY clause.

       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 USING clause.  Which technique is more appropriate depends on the spe-
       cific circumstances.

       The optional RETURNING clause causes DELETE 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 USING, can be computed.  The syntax of
       the RETURNING list is identical to that of the output list of SELECT.

       You must have the DELETE privilege on the table to delete from it, as well as the SELECT privilege for any table  in  the
       USING clause or whose values are read in the condition.

PARAMETERS
       ONLY   If  specified, delete rows from the named table only. When not specified, any tables inheriting from the named ta-
              ble are also processed.

       table  The name (optionally schema-qualified) of an existing table.

       alias  A substitute name for the target table. When an alias is provided, it completely hides the actual name of the  ta-
              ble.  For example, given DELETE FROM foo AS f, the remainder of the DELETE statement must refer to this table as f
              not foo.

       usinglist
              A list of table expressions, allowing columns from other tables to appear in the WHERE condition. This is  similar
              to  the list of tables that can be specified in the FROM Clause [select(7)] of a SELECT statement; for example, an
              alias for the table name can be specified. Do not repeat the target table in the usinglist, unless you wish to set
              up a self-join.

       condition
              An  expression  that  returns  a  value of type boolean.  Only rows for which this expression returns true will be
              deleted.

       cursor_name
              The name of the cursor to use in a WHERE CURRENT OF 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 DELETE's target table.  Note that WHERE
              CURRENT OF cannot be specified together with a Boolean condition. See DECLARE [declare(7)]  for  more  information
              about using cursors with WHERE CURRENT OF.

       output_expression
              An  expression to be computed and returned by the DELETE command after each row is deleted. The expression can use
              any column names of the table or table(s) listed in USING.  Write * to return all columns.

       output_name
              A name to use for a returned column.

OUTPUTS
       On successful completion, a DELETE command returns a command tag of the form

       DELETE count

       The count is the number of rows deleted. If count is 0, no rows matched the condition (this is not considered an error).

       If the DELETE command contains a RETURNING clause, the result will be similar to that of a  SELECT  statement  containing
       the columns and values defined in the RETURNING list, computed over the row(s) deleted by the command.

NOTES
       PostgreSQL  lets you reference columns of other tables in the WHERE condition by specifying the other tables in the USING
       clause. For example, to delete all films produced by a given producer, one can do:

       DELETE FROM films USING producers
         WHERE producer_id = producers.id AND producers.name = 'foo';

       What is essentially happening here is a join between films and producers, with all successfully joined films  rows  being
       marked for deletion.  This syntax is not standard. A more standard way to do it is:

       DELETE FROM films
         WHERE producer_id IN (SELECT id FROM producers WHERE name = 'foo');

       In some cases the join style is easier to write or faster to execute than the sub-select style.

EXAMPLES
       Delete all films but musicals:

       DELETE FROM films WHERE kind <> 'Musical';


       Clear the table films:

       DELETE FROM films;


       Delete completed tasks, returning full details of the deleted rows:

       DELETE FROM tasks WHERE status = 'DONE' RETURNING *;


       Delete the row of tasks on which the cursor c_tasks is currently positioned:

       DELETE FROM tasks WHERE CURRENT OF c_tasks;


COMPATIBILITY
       This command conforms to the SQL standard, except that the USING and RETURNING clauses are PostgreSQL extensions.



SQL - Language Statements                                  2011-09-22                                                  DELETE(7)