DELETE(7)

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 [ WITH ( { OLD | NEW } AS output_alias [, ...] ) ]
                { * | 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 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_alias
    An optional substitute name for OLD or NEW rows in the RETURNING list.

    By default, old values from the target table can be returned by writing OLD.column_name or OLD.*, and new values can be returned by writing NEW.column_name or NEW.*. When an alias is provided, these names are hidden and the old or new rows must be referred to using the alias. For example RETURNING WITH (OLD AS o, NEW AS n) o.*, n.*.

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.

    A column name or * may be qualified using OLD or NEW, or the corresponding output_alias for OLD or NEW, to cause old or new values to be returned. An unqualified column name, or *, or a column name or * qualified using the target table name or alias will return old values.

    For a simple DELETE, all new values will be NULL. However, if an ON DELETE rule causes an INSERT or UPDATE to be executed instead, the new values may be non-NULL.

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;

While there is no LIMIT clause for DELETE, it is possible to get a similar effect using the same method described in the documentation of UPDATE:

    WITH delete_batch AS (
      SELECT l.ctid FROM user_logs AS l
        WHERE l.status = 'archived'
        ORDER BY l.creation_date
        FOR UPDATE
        LIMIT 10000
    )
    DELETE FROM user_logs AS dl
      USING delete_batch AS del
      WHERE dl.ctid = del.ctid;

This use of ctid is only safe because the query is repeatedly run, avoiding the problem of changed ctids.

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)