delete(7) - phpMan

DELETE()                                   SQL Commands                                  DELETE()



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 mecha-
              nism 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 specific 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 table 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 table. 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
              simple  (non-join,  non-aggregate)  query  on the DELETE's target table.  Note that
              WHERE CURRENT OF cannot be specified together with a Boolean condition.

       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 suc-
       cessfully 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()

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