DELETE
SQL - Language Statements
DELETE
delete rows of a table
DELETE
DELETE FROM [ ONLY ] table [ 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.
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 subtables. If you wish to delete only
from the specific table mentioned, you must use the
ONLY clause.
You must have the DELETE privilege on the table
to delete from it, as well as the SELECT
privilege for any table whose values are read in the condition.
Parameters
table
The name (optionally schema-qualified) of an existing table.
condition
A value expression that returns a value of type
boolean that determines the rows which 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. For example, to
delete all films produced by a given producer, one might do
DELETE FROM films
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. One objection to the join style
is that there is no explicit list of what tables are being used,
which makes the style somewhat error-prone; also it cannot handle
self-joins.
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 ability to
reference other tables in the WHERE> clause is a
PostgreSQL extension.