DELETE

Like UPDATE, the DELETE command is simple. The general format of the DELETE command is

DELETE FROM table [ WHERE condition ]

The DELETE command removes all rows that satisfy the (optional) WHERE clause. Here is an example:

movies=# SELECT * FROM tapes;

 tape_id  |        title         | duration

----------+----------------------+----------

 AB-12345 | The Godfather        |

 AB-67472 | The Godfather        |

 MC-68873 | Casablanca           |

 OW-41221 | Citizen Kane         |

 AH-54706 | Rear Window          |

 OW-42200 | Sly                  | 01:36

 KJ-03335 | American Citizen, An |

 OW-42201 | Stone Cold           | 01:52

(8 rows)

movies=# BEGIN WORK;

BEGIN

movies=# DELETE FROM tapes WHERE duration IS NULL;

DELETE 6

movies=# SELECT * FROM tapes;

 tape_id  |   title    | duration

----------+------------+----------

 OW-42200 | Sly        | 01:36

 OW-42201 | Stone Cold | 01:52

(2 rows)



movies=# ROLLBACK;

ROLLBACK

Before we executed the DELETE command, there were eight rows in the tapes table, and six of these tapes had a NULL duration.

You can see that the DELETE statement returns the number of rows deleted ("DELETE 6"). After the DELETE statement, only two tapes remain.

If you omit the WHERE clause in a DELETE command, PostgreSQL will delete all rows. Similarly, forgetting the WHERE clause for an UPDATE command updates all rows. Be careful!