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Sams Teach Yourself SQL in 10 Minutes, Fourth Edition by Ben Forta

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Lesson 22. Understanding Advanced SQL Features

In this lesson, you’ll look at several of the advanced data-manipulation features that have evolved with SQL: constraints, indexes, and triggers.

Understanding Constraints

SQL has evolved through many versions to become a very complete and powerful language. Many of the more powerful features are sophisticated tools that provide you with data-manipulation techniques such as constraints.

Relational tables and referential integrity have both been discussed several times in prior lessons. As I explained in those lessons, relational databases store data broken into multiple tables, each of which stores related data. Keys are used to create references from one table to another (thus the term referential ...

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