MySQL User defined Variables – good thing to know!
Have you ever heard of user defined variables in MySQL? I hadn’t and nearly freaked out when I found out. That’s the thing I was always looking for, that’s so cool, and fasten up your SQL live a lot!
Now, renumbering a table is as easy as never before:
Set @a = 0;
UPDATE my_table SET id=@a:=@a+1
Check out the docu and examples: