I got tired looking for a good solution to imitate a rownum in MySQL every time I need it. Here I post the most
universal solution that doesn’t need a script mode and can be executed in a single statement:

SELECT @rownum:=@rownum+1 rownum, t.*
FROM (SELECT @rownum:=0) r, mytable t;
 

This solution and others you can find in comments to the MySQL Reference Manual.