DELETE

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

DELETEdeletes rows that satisfy theWHEREclause from the specified table. If theWHEREclause is absent, the effect is to delete all rows in the table. The result is a valid, but empty table.

Tip

TRUNCATEprovides 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 theUSINGclause. Which technique is more appropriate depends on the specific circumstances.

The optionalRETURNINGclause causesDELETEto 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 inUSING, can be computed. The syntax of theRETURNINGlist is identical to that of the output list ofSELECT.

You must have theDELETEprivilege on the table to delete from it, as well as theSELECTprivilege for any table in theUSINGclause or whose values are read in thecondition.

Parameters

with_query

TheWITHclause allows you to specify one or more subqueries that can be referenced by name in theDELETEquery. SeeSection 7.8andSELECTfor details.

table_name

The name (optionally schema-qualified) of the table to delete rows from. IfONLYis specified before the table name, matching rows are deleted from the named table only. IfONLYis 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, givenDELETE FROM foo AS f, the remainder of theDELETEstatement must refer to this table asfnotfoo.

using_list

A list of table expressions, allowing columns from other tables to appear in theWHEREcondition. This is similar to the list of tables that can be specified in theFROMClauseof aSELECTstatement; for example, an alias for the table name can be specified. Do not repeat the target table in theusing_list, unless you wish to set up a self-join.

condition

An expression that returns a value of typeboolean. Only rows for which this expression returnstruewill be deleted.

cursor_name

The name of the cursor to use in aWHERE CURRENT OFcondition. The row to be deleted is the one most recently fetched from this cursor. The cursor must be a non-grouping query on theDELETE's target table. Note thatWHERE CURRENT OFcannot be specified together with a Boolean condition. SeeDECLAREfor more information about using cursors withWHERE CURRENT OF.

output_expression

An expression to be computed and returned by theDELETEcommand after each row is deleted. The expression can use any column names of the table named by_table_name_or table(s) listed inUSING. Write*to return all columns.

output_name

A name to use for a returned column.

Outputs

On successful completion, aDELETEcommand returns a command tag of the form

DELETE
count

Thecount_is the number of rows deleted. Note that the number may be less than the number of rows that matched theconditionwhen deletes were suppressed by aBEFORE DELETEtrigger. Ifcount_is 0, no rows were deleted by the query (this is not considered an error).

If theDELETEcommand contains aRETURNINGclause, the result will be similar to that of aSELECTstatement containing the columns and values defined in theRETURNINGlist, computed over the row(s) deleted by the command.

Notes

PostgreSQLlets you reference columns of other tables in theWHEREcondition by specifying the other tables in theUSINGclause. 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 betweenfilmsandproducers, with all successfully joinedfilmsrows 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 tablefilms:

DELETE FROM films;

Delete completed tasks, returning full details of the deleted rows:

DELETE FROM tasks WHERE status = 'DONE' RETURNING *;

Delete the row oftaskson which the cursorc_tasksis currently positioned:

DELETE FROM tasks WHERE CURRENT OF c_tasks;

Compatibility

This command conforms to theSQLstandard, except that theUSINGandRETURNINGclauses arePostgreSQLextensions, as is the ability to useWITHwithDELETE.

See Also

TRUNCATE