|The PostgreSQL 9.0 Reference Manual - Volume 1B - SQL Command Reference
by The PostgreSQL Global Development Group
Paperback (6"x9"), 488 pages
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DELETE -- delete rows of a table
DELETE FROM [ ONLY ] table [ [ AS ] alias ] [ USING using_list ] [ WHERE condition | WHERE CURRENT OF cursor_name ] [ RETURNING * | output_expression [ [ AS ] output_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.
TRUNCATEis a PostgreSQL extension that provides a faster mechanism to remove all rows from a table.
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
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
Which technique is more appropriate depends on the specific
RETURNING clause causes
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
You must have the
DELETE privilege on the table
to delete from it, as well as the
privilege for any table in the
USING clause or
whose values are read in the condition.
- If specified, delete rows from the named table only. When not specified, any tables inheriting from the named table are also processed.
- The name (optionally schema-qualified) of an existing table.
A substitute name for the target table. When an alias is
provided, it completely hides the actual name of the table. For
DELETE FROM foo AS f, the remainder of the
DELETEstatement must refer to this table as
A list of table expressions, allowing columns from other tables
to appear in the
WHEREcondition. This is similar to the list of tables that can be specified in the FROM Clause of a
SELECTstatement; for example, an alias for the table name can be specified. Do not repeat the target table in the using_list, unless you wish to set up a self-join.
An expression that returns a value of type
boolean. Only rows for which this expression returns
truewill be deleted.
The name of the cursor to use in a
WHERE 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 the
DELETE's target table. Note that
WHERE CURRENT OFcannot be specified together with a Boolean condition. See
DECLAREfor more information about using cursors with
WHERE CURRENT OF.
An expression to be computed and returned by the
DELETEcommand after each row is deleted. The expression can use any column names of the table or table(s) listed in
*to return all columns.
- A name to use for a returned column.
On successful completion, a
DELETE command returns a command
tag of the form
The count is the number of rows deleted. If count is 0, no rows matched the condition (this is not considered an error).
DELETE command contains a
clause, the result will be similar to that of a
statement containing the columns and values defined in the
RETURNING list, computed over the row(s) deleted by the
PostgreSQL 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 do:
DELETE FROM films USING producers WHERE producer_id = producers.id AND producers.name = 'foo';
What is essentially happening here is a join between
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.
Delete all films but musicals:
DELETE FROM films WHERE kind <> 'Musical';
Clear the table
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;
This command conforms to the SQL standard, except
are PostgreSQL extensions.
|ISBN 9781906966058||The PostgreSQL 9.0 Reference Manual - Volume 1B - SQL Command Reference||See the print edition|