DELETE

Deletes rows from 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 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.

Note
The RETURNING clause is not supported when deleting from append-optimized tables.

Note
As the default, Greenplum Database acquires an EXCLUSIVE lock on tables for DELETE operations on heap tables. When the Global Deadlock Detector is enabled, the lock mode for DELETE operations on heap tables is ROW EXCLUSIVE. See Global Deadlock Detector.

Parameters

with_query: The WITH clause allows you to specify one or more subqueries that can be referenced by name in the DELETE query.; For a DELETE command that includes a WITH clause, the clause can only contain SELECT statements, the WITH clause cannot contain a data-modifying command (INSERT, UPDATE, or DELETE).; See WITH Queries (Common Table Expressions) and SELECT for details.
table_name: The name (optionally schema-qualified) of the table to delete rows from. If you specify ONLY before the table name, Greenplum Database deletes matching rows from the named table only. If ONLY is not specified, matching rows are also deleted from any tables inheriting from the named table. Optionally, you can specify * 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, you can specify an alias for the table name. Do not repeat the target table in the 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. Greenplum Database deletes only those rows for which this expression returns true.
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 for more information about using cursors with WHERE CURRENT OF.; The DELETE...WHERE CURRENT OF cursor statement can only be run 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.
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. 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

The RETURNING clause is not supported when deleting from append-optimized tables.

The WHERE CURRENT OF clause is not supported with replicated tables.

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 delete all films produced by a given producer, one can run:

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 accomplish this is:

DELETE FROM films
  WHERE producer_id IN (SELECT id FROM producers WHERE name = 'foo');

For a partitioned table, all of the child tables are locked during the DELETE operation when the Global Deadlock Detector is not enabled (the default). Only some of the leaf child tables are locked when the Global Deadlock Detector is enabled. For information about the Global Deadlock Detector, see Global Deadlock Detector.

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;

Delete using a join:

DELETE FROM rank USING names WHERE names.id = rank.id AND 
name = 'Hannah';

Compatibility

This command conforms to the SQL standard, except that the USING and RETURNING clauses are Greenplum Database extensions, as is the ability to use WITH with DELETE.