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DELETE()			 SQL Commands			      DELETE()

       DELETE - delete rows of a table

       DELETE FROM [ ONLY ] table
	   [ USING usinglist ]
	   [ WHERE condition ]

       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 pro-
	      vides 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 men-
       tioned, you must use the ONLY clause.

       There are two ways to delete rows in a  table  using  information  con-
       tained  in other tables in the database: using sub-selects, or specify-
       ing additional tables in the USING clause.   Which  technique  is  more
       appropriate depends on the specific circumstances.

       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.

       ONLY   If  specified,  delete  rows from the named table only. When not
	      specified, any tables inheriting from the named table  are  also

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

	      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.

	      An expression returning a value of type  boolean,	 which	deter-
	      mines the rows that are to be deleted.

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

       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).

       PostgreSQL lets you reference columns of other tables in the WHERE con-
       dition by specifying the other tables in the USING clause. For example,
       to delete all films produced by a given producer, one might 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 produc-
       ers, 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.

       Delete all films but musicals:

       DELETE FROM films WHERE kind <> 'Musical';

       Clear the table films:

       DELETE FROM films;

       This command conforms to the SQL standard, except that the USING clause
       and the ability to reference other tables in the WHERE clause are Post-
       greSQL extensions.

SQL - Language Statements	  2010-12-14			      DELETE()