Question

Is it better to store an integer UserID or store Username as the key.

Which is better for performance?

Answer 1

The questions seems more like a discussion because it’s really based on application requirements. However, I will give a general answer why UserID is better for performance.

My 3 reasons why UserID is better for performance:

1. Can be auto incremented saving one less trip to database to check if Username is in use.
2. Allows for users to change usernames
3. Unsigned INT data type only requires up to 4 bytes allowing up to 4294967295 unique ids

My 3 reasons not to use Username:

1. Storage, using an UTF-8 charset will require 3 bytes per character or 1 byte per character for something like latin1
2. For maximum lookup speed, you have to use MyISAM table with fixed-width tables. A fixed-width table on MyISAM gives you a 30% increase in lookup speed versus a dynamic table.
3. MyISAM does table level locking which can cause slower performance if table is a heavy write.