Specifications

Using MySQL

ART II

208

In this chapter, we’ll discuss Structured Query Language (SQL) and its use in querying data-

bases. We’ll continue developing the Book-O-Rama database by seeing how to insert, delete,

and update data, and how to ask the database questions.

Topics we will cover include

• What is SQL?

• Inserting data into the database

• Retrieving data from the database

• Joining tables

• Updating records from the database

• Altering tables after creation

• Deleting records from the database

• Dropping tables

We’ll begin by talking about what SQL is and why it’s a useful thing to understand.

If you haven’t set up the Book-O-Rama database, you’ll need to do that before you can run the

SQL queries in this chapter. Instructions for doing this are in Chapter 8, “Creating Your Web

Database.”

What Is SQL?

SQL stands for Structured Query Language. It’s the most standard language for accessing rela-

tional database management systems (RDBMS). SQL is used to store and retrieve data to and

from a database. It is used in database systems such as MySQL, Oracle, PostgreSQL, Sybase,

and Microsoft SQL Server among others.

There’s an ANSI standard for SQL, and database systems such as MySQL implement this stan-

dard. They also typically add some bells and whistles of their own. The privilege system in

MySQL is one of these.

You might have heard the phrases Data Definition Languages (DDL), used for defining data-

bases, and Data Manipulation Languages (DML), used for querying databases. SQL covers

both of these bases. In Chapter 8, we looked at data definition (DDL) in SQL, so we’ve already

been using it a little. You use DDL when you’re initially setting up a database.

You will use the DML aspects of SQL far more frequently because these are the parts that we

use to store and retrieve real data in a database.

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