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 ...