title: What is the effect of using auto increment key in a database?
body: <p>When i consider the structure of table, i'm hesitating if i should use the <code>auto increment key</code> as the primary key in my table. I can't find the good effect of using the auto increment key and the bad effect of not using auto increment key. Someone say use <code>auto increment key</code> can increase the query performance. Is that right?</p>