Question

Greetings,

I have some mysql tables that are currently using an md5 hash as a primary key. I normally generate the hash with the value of a column. For instante, let’s imagine I have a table called “Artists” with the fields id, name, num_members, year. I tend to make a md5($name) and use it has an ID.

I would like to know what are the downsides of doing this. Is it just better to use integers with AUTO_INCREMENT ? I tend to run away from this because it’s just not worth the trouble of finding out what the last id inserted was, and what will be the next etc.

Can you give me some lights on this?

Thank you.

Answer 1

If you need a surrogate primary key, using an AUTO_INCREMENT field is better than an md5 hash, because it is fewer bytes of data, and database backends optimize for integer primary keys.

mysql_insert_id can be used if you need the last inserted id.

If you are generating the primary key as a hash of other columns, why not just use those other columns as a unique key, then join on those?

Another question is, what are the upsides of using an md5 hash? I can’t think of any.