MySQL Cookbook

Chapter 3. Record Selection Techniques

Introduction

This chapter focuses on the SELECT statement that is used for retrieving information from a database. It provides some essential background that shows various ways you can use SELECT to tell MySQL what you want to see. You should find the chapter helpful if your SQL background is limited or if you want to find out about the MySQL-specific extensions to SELECT syntax. However, there are so many ways to write SELECT queries that we’ll necessarily touch on just a few. You may wish to consult the MySQL Reference Manual or a MySQL text for more information about the syntax of SELECT, as well as the functions and operators that you can use for extracting and manipulating data.

SELECT gives you control over several aspects of record retrieval:

• Which table to use

• Which columns to display from the table

• What names to give the columns

• Which rows to retrieve from the table

• How to sort the rows

Many useful queries are quite simple and don’t specify all those things. For example, some forms of SELECT don’t even name a table—a fact used in Recipe 1.32, which discusses how to use mysql as a calculator. Other non-table-based queries are useful for purposes such as checking what version of the server you’re running or the name of the current database:

mysql> SELECT VERSION( ), DATABASE( );
+-------------+------------+
| VERSION( )   | DATABASE( ) |
+-------------+------------+
| 3.23.51-log | cookbook   |
+-------------+------------+

However, to answer more ...