Index for Section 5

Alphabetical listing for D

Bottom of page

DELETE()
NAME
  DELETE - delete rows of a table

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

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(5)] 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 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.

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.

  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(5)] 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 returning a value of type boolean, which determines the
       rows that are to be deleted.

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).

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 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 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;

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

Index for Section 5

Alphabetical listing for D

Top of page