在PHP / Mysql中生成随机数作为主键

Question

What is the best way to generate alphanumeric random number to 8 digit in php which is case sensitive? I want to use this unique number to be stored in mysql data base and make it a primary key.

Answer 1

Never use a random key as primary key. Primary keys need to be unique in most cases and random numbers are not.

E.g.

1 1 1 1 1 1 0 1 

is also a valid output of a 8 digit random number generator.

You should use auto-increment fields or generators instead to make sure that your primary key is really unique.

If you want to have a identifier which is likely to be unique and some sort of random try to use mysql facilities like: http://dev.mysql.com/doc/refman/5.0/en/miscellaneous-functions.html#function_uuid

A caveat might be to reiterate inserts multiple times.