Question

I am trying to figure out how to do a table with 3 columns:

unique_id, type, version

Where unique_id is AUTO_INCREMENT for each record, and version is AUTO_INCREMENT for each type.

The purpose being, when I insert I only have to specify ‘type’ and the unique_id and version_id are automatically generated. eg:

insert type 'a', then values are:  1 , a , 1
insert type 'a', then values are:  2 , a , 2
insert type 'a', then values are:  3 , a , 3
insert type 'b', then values are:  4 , b , 1
insert type 'b', then values are:  5 , b , 2
insert type 'a', then values are:  6 , a , 4

Also would it be fair to say that such a setup is not really normalised? That instead it should be two tables?

Answer 1

You can’t have auto-generated sequences for each type, but you can generate your own.

insert into the_table (type, version)
select 'a', 1 + IFNULL(max(version), 0)
  from the_table
  where type = 'a';