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SQL in a Nutshell, 3rd Edition
book

SQL in a Nutshell, 3rd Edition

by Kevin Kline
November 2008
Intermediate to advanced content levelIntermediate to advanced
591 pages
17h 28m
English
O'Reilly Media, Inc.
Content preview from SQL in a Nutshell, 3rd Edition

Constraints

Constraints allow you to automatically enforce the integrity of data and to filter the data that is placed in a database. In a sense, constraints are rules that define which data values are valid during INSERT, UPDATE, and DELETE operations. When a data-modification transaction breaks the rules of a constraint, the transaction is rejected.

In the ANSI standard, there are four constraint types: CHECK, PRIMARY KEY, UNIQUE, and FOREIGN KEY. (The RDBMS platforms may allow more; refer to Chapter 3 for details.)

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Publisher Resources

ISBN: 9780596155322Errata Page