PHP & MySQL® Web Development All-in-One Desk Reference for Dummies®

4.5. Removing Information from a Database

Keep the information in your database up to date by deleting obsolete information. However, be very careful when removing information. After you drop the data, it's gone forever. It cannot be restored. You only get it back if you enter it all again.

4.5.1. Removing information with an SQL query

You can remove a row or a column from a table, or you can remove the entire table or database and start over.

You can remove a row from a table with the DELETE query:

DELETE FROM tablename WHERE clause

Be extremely careful when using DELETE. If you use a DELETE query without a WHERE clause, it will delete all the data in the table. We mean all the data. We repeat, all the data. The data cannot be recovered. This function of the DELETE query is right at the top of our don't-try-this-at-home list.

You can delete a column from a table by using the ALTER query:

ALTER TABLE tablename DROP columnname

You can remove the entire table or database with

DROP TABLE tablename

or

DROP DATABASE databasename

4.5.2. Removing information with phpMyAdmin

The Database page in phpMyAdmin lists all the tables in a database. You can display the Database page by clicking the database name in the left panel or by selecting the database name from the Database drop-down list. From this page, you can delete the entire database or any table as follows:

• Database: Drop the ...