Deletes rows from a table.
DELETE FROM [ONLY] <table> [[AS] <alias>]
[USING <usinglist>]
[WHERE <condition> | WHERE CURRENT OF <cursor_name> ]
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.
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.
If the WHERE CURRENT OF
clause is specified, the row that is deleted is the one most recently fetched from the specified cursor.
You must have the DELETE
privilege on the table to delete from it.
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).
DELETE FROM foo AS f
, the remainder of the
DELETE
statement must refer to this table as
f
not
foo
.
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
usinglist
, unless you wish to set up a self-join.
boolean
, which determines the rows that are to be deleted.
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 simple (non-join, non-aggregate) query on the DELETE
target table.
WHERE CURRENT OF
cannot be specified together with a Boolean condition.
The DELETE...WHERE CURRENT OF
cursor statement can only be executed on the server, for example in an interactive psql session or a script. Language extensions such as PL/pgSQL do not have support for updatable cursors.
Greenplum Database lets you reference columns of other tables in the WHERE
condition by specifying the other tables in the USING
clause. For example, to the name Hannah
from the rank
table, one might do:
DELETE FROM rank USING names WHERE names.id = rank.id AND
name = 'Hannah';
What is essentially happening here is a join between rank
and names
, with all successfully joined rows being marked for deletion. This syntax is not standard. However, this join style is usually easier to write and faster to execute than a more standard sub-select style, such as:
DELETE FROM rank WHERE id IN (SELECT id FROM names WHERE name
= 'Hannah');
Execution of UPDATE
and DELETE
commands directly on a specific partition (child table) of a partitioned table is not supported. Instead, these commands must be executed on the root partitioned table, the table created with the CREATE TABLE
command.
For a partitioned table, all the child tables are locked during the DELETE
operation.
Delete all films but musicals:
DELETE FROM films WHERE kind <> 'Musical';
Clear the table films:
DELETE FROM films;
Delete using a join:
DELETE FROM rank USING names WHERE names.id = rank.id AND
name = 'Hannah';
This command conforms to the SQL standard, except that the USING
clause is a Greenplum Database extension.
Parent topic: SQL Command Reference