MySQL: Auto increment temporary column in select statement

Question

How do I create and auto increment a temporary column in my select statement with MySQL?

Here is what I have so far:

SET @cnt = 0;
SELECT
    (@cnt          


        

Answer 1

But what if you have a group by in the select statement? the counting will be off.

For such cases, the only solution I found is nesting select:

SELECT (@cnt := @cnt + 1) AS rowNumber, t.*
from
(select
    t.rowID
FROM myTable 
WHERE CategoryID = 1
ORDER BY rowID) t
CROSS JOIN (SELECT @cnt := 0) AS dummy