Introduction

SQL is the standard programming language for creating, updating, and retrieving information that is stored in databases. With SQL, you can turn your ordinary questions (“Where do our customers live?”) into statements that your database system can understand (SELECT DISTINCT city, state FROM customers;). You might already know how to extract this type of information by using a graphical query or reporting tool, but perhaps you've noticed that this tool becomes limiting or cumbersome as your questions grow in complexity—that's where SQL comes in.

You also can use SQL to add, change, and delete data and database objects. All modern relational database management systems (DBMSes) support SQL, although support varies by product (more about ...

Get SQL: Visual Quickstart Guide, Second Edition now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.