DELETE(7)
NAME
DELETE - delete rows of a table
SYNOPSIS
[ WITH [ RECURSIVE ] with_query [, ...] ]
DELETE FROM [ ONLY ] table_name [ * ] [ [ AS ] alias ]
[ USING using_list ]
[ 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) is a PostgreSQL extension that 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,
"WITH Queries (Common Table Expressions)", in the documentation 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.
using_list
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 of a SELECT
statement; for example, an alias for the table name can be
specified. Do not repeat the target table in the using_list, 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 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.
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