MySQL: what is a temporary table?

Question

What is the purpose of a temporary table like in the following statement? How is it different than a regular table?

CREATE TEMPORARY TABLE tmptable
SELECT A.* FROM batchinfo_2009 AS A, calibration_2009 AS B
WHERE A.reporttime LIKE '%2010%'
AND A.rowid = B.rowid;

Answer 1

Temp tables are kept only for the duration of your session with the sever. Once the connection's severed for any reason, the table's automatically dropped. They're also only visible to the current user, so multiple users can use the same temporary table name without conflict.

Answer 2

Temporary table ceases to exist when connection is closed. So, its purpose is for instance to hold temporary result set that has to be worked on, before it will be used.

Answer 3

Temporary tables are mostly used to store query results that need further processing, for instance if the result needs to be queried or refined again or is going to be used at different occasions by your application. Usually the data stored in a temporary database contains information from several regular tables (like in your example).

Temporary tables are deleted automatically when the current database session is terminated.