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!

Part I: General PostgreSQL Use

Introduction to PostgreSQL and SQL

Working with Data in PostgreSQL

PostgreSQL SQL Syntax and Use

Performance

Part II: Programming with PostgreSQL

Introduction to PostgreSQL Programming

Extending PostgreSQL

PL/pgSQL

The PostgreSQL C APIlibpq

A Simpler C APIlibpgeasy

The New PostgreSQL C++ APIlibpqxx

Embedding SQL Commands in C Programsecpg

Using PostgreSQL from an ODBC Client Application

Using PostgreSQL from a Java Client Application

Using PostgreSQL with Perl

Using PostgreSQL with PHP

Using PostgreSQL with Tcl and Tcl/Tk

Using PostgreSQL with Python

Npgsql: The .NET Data Provider

Other Useful Programming Tools

Part III: PostgreSQL Administration

Introduction to PostgreSQL Administration

PostgreSQL Administration

Internationalization and Localization

Security

Replicating PostgreSQL Data with Slony

Contributed Modules

Index



PostgreSQL(c) The comprehensive guide to building, programming, and administering PostgreSQL databases
PostgreSQL(c) The comprehensive guide to building, programming, and administering PostgreSQL databases
ISBN: 735712573
EAN: N/A
Year: 2004
Pages: 261

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