MySQL Cookbook

Creating Temporary Tables

Problem

You need a table only for a short time, then you want it to disappear automatically.

Solution

Create a TEMPORARY table and let MySQL take care of clobbering it.

Discussion

Some operations require a table that exists only temporarily and that should disappear when it’s no longer needed. You can of course issue a DROP TABLE statement explicitly to remove a table when you’re done with it. Another option, available in MySQL 3.23.2 and up, is to use CREATE TEMPORARY TABLE. This statement is just like CREATE TABLE except that it creates a transient table that disappears when your connection to the server closes, if you haven’t already removed it yourself. This is extremely useful behavior because you need not remember to remove the table. MySQL drops it for you automatically.

Temporary tables are connection-specific, so several clients each can create a temporary table having the same name without interfering with each other. This makes it easier to write applications that use transient tables, because you need not ensure that the tables have unique names for each client. (See Recipe 3.27 for further discussion of this issue.)

Another property of temporary tables is that they can be created with the same name as a permanent table. In this case, the temporary table “hides” the permanent table for the duration of its existence, which can be useful for making a copy of a table that you can modify without affecting the original by mistake. The DELETE statement ...