bionic (7) DELETE.7.gz

NAME

       DELETE - delete rows of a table

SYNOPSIS

       [ WITH [ RECURSIVE ] with_query [, ...] ]
       DELETE FROM [ ONLY ] table_name [ * ] [ [ AS ] alias ]
           [ USING from_item [, ...] ]
           [ 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(7) provides a faster mechanism to remove all rows from a table.

       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

       with_query
           The WITH clause allows you to specify one or more subqueries that can be referenced by name in the
           DELETE query. See Section 7.8 and SELECT(7) for details.

       table_name
           The name (optionally schema-qualified) of the table to delete rows from. If ONLY is specified before
           the table name, matching rows are deleted from the named table only. If ONLY is not specified,
           matching rows are also deleted from any tables inheriting from the named table. Optionally, * can be
           specified after the table name to explicitly indicate that descendant tables are included.

       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.

       from_item
           A table expression allowing columns from other tables to appear in the WHERE condition. This uses the
           same syntax as the FROM Clause of a SELECT statement; for example, an alias for the table name can be
           specified. Do not repeat the target table as a from_item unless you wish to set up a self-join (in
           which case it must appear with an alias in the from_item).

       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(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 named by table_name 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. Note that the number may be less than the number of rows that
       matched the condition when deletes were suppressed by a BEFORE DELETE trigger. If count is 0, no rows
       were deleted by the query (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, as is the ability to use WITH with DELETE.

SEE ALSO

       TRUNCATE(7)