DELETE
DELETE — Delete rows of 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 empty 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 columns of the deleted table, 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.
To delete rows from a table, you must have the DELETE privilege on it, as well as the SELECT privilege on any table in the USING clause and any table 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 within the DELETE query.
table_name
The name (optionally schema-qualified) of the table from which to delete rows. 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 will refer to the table as f instead of 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 SELECT; for example, aliases for table names can be specified. Do not repeat the target table as a 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. 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 most recently fetched from this cursor will be deleted. The cursor must be a non-grouped query on the DELETE target table. Note that you cannot specify a Boolean condition together with WHERE CURRENT OF. See DECLARE 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 of the table named by table_name or tables listed in USING. Write * to return all columns.
output_name
The name to use for a returned column.
Output
On successful completion, a DELETE command returns a command tag of the following form:
DELETE count
count is the number of rows deleted. Note that the number may be less than the number of rows matching condition if a BEFORE DELETE trigger suppressed the deletion. 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 rows deleted by the command.
Notes
By specifying other tables in the USING clause, the system allows columns of other tables to be referenced in the WHERE condition. For example, to delete all films produced by a given producer, you could do:
DELETE FROM films USING producers
WHERE producer_id = producers.id AND producers.name = 'foo';
What essentially happens here is a join between films and producers, with all successfully joined films rows being deleted. 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 may execute faster than the subquery style.
Examples
# Delete all films except musicals:
DELETE FROM films WHERE kind <> 'Musical';
# Clear the table films:
DELETE FROM films;
# Delete completed tasks, returning details of the deleted rows:
DELETE FROM tasks WHERE status = 'DONE' RETURNING *;
# Delete the row in tasks on which the cursor c_tasks is currently positioned:
DELETE FROM tasks WHERE CURRENT OF c_tasks;