Question

I have a simple users table, I guess the maximum users I am going to have is 300,000.

Currently I am using:

 CREATE TABLE users
 (
         id INT UNSIGNED AUTOINCREMENT PRIMARY KEY,
         ....

Of course I have many other tables for which users(id) is a FOREIGN KEY.

I read that since the id is not going to use the full maximum of INT it is better to use:
MEDIUMINT and it will give better performance.

Is it true?

(I am using mysql on Windows Server 2008)

Answer 1

I would consider using MEDIUMINT sometimes.. on 300K rows.. MEDIUMINT gives u enough room up to 16M rows (unsigned).

It is not only about “smaller table size” when u use indexes.. the difference can be huge
on a 27M rows tables.. changing 2 columns from INT to MEDIUMINT saved me 1GB (indexes + table data) so it went from 2.5GB to 1.5 GB.