Deleting Stored Data

Deleting Stored Data

The deletion of entries in SQL is dangerously easy, which, if you haven't noticed

yet, is a recurring theme. Here's the command syntax:

mysql>DELETE FROM table_name WHERE conditons;

So to delete all chicken jokes from your table, you'd use the following query:

mysql>DELETE FROM Jokes WHERE JokeText LIKE "%chicken%";

One thing to note is that the WHERE clause is actually optional. You should be

very careful, however, if you leave it off, as the DELETE command will then apply

to all entries in the table. This command will empty the Jokes table in one fell

swoop:

mysql>DELETE FROM Jokes;

Scary, huh?

Summary

There's a lot more to the MySQL database system and the SQL language than

the few basic commands we've looked at here, but these commands are by far

the most commonly used. So far we've only worked with a single table. To realize

the true power of a relational database, we'll also need to learn how to use multiple

tables together to represent potentially complex relationships between database

entities.

We'll cover all this and more in Chapter 5, where we'll discuss database design

principles, and look at some more advanced examples. For now, though, we've

accomplished our objective, and you can comfortably interact with MySQL using

the command line interface. In Chapter 3, the fun continues as we delve into the

PHP server-side scripting language, and use it to create dynamic Web pages. If

you like, you can practice with MySQL a little before you move on, by creating

a decent-sized Jokes table — this knowledge will come in handy in Chapter 4!

Deleting Stored Data