MySQL keep type in case statement - mysql

Question

I have a field that changes based on some input:
SELECT
CASE input
WHEN 1 THEN id
WHEN 2 THEN created_at
WHEN 3 THEN some_varchar_field
END as test
FROM ...
ORDER BY 1 ASC;
If I were to order by this field any numeric field isn't sorted properly, I noticed that the order by doesn't keep the type of the field that was selected rather, as soon as there is a VARCHAR/DATETIME field it will return that type rather then keep the type of the column itself. I was just wondering if there was a way to keep the type of the record that was selected.
Edit: Casting field as an int CAST(id as INT) did not work
Putting the case statement in the order by did not work as well.

Answer 1

I think on this solution, isn't pretty but should work.
SQL Fiddle Demo
Create a new column for each of your fields with the order on it.
SELECT CASE 1
WHEN 1 THEN id
WHEN 2 THEN created_at
WHEN 3 THEN scomment
END as field_name
FROM (
SELECT I.id, I.rid,
C.created_at, C.rcreated_at,
S.scomment, S.rscomment
FROM (
SELECT t.id,
#rowid := #rowid + 1 AS rid
FROM test t,
(SELECT #rowid := 0) r
ORDER BY t.id
) I -- add sort column for id
JOIN (
SELECT t.id, created_at,
#rowcreated_at := #rowcreated_at + 1 AS rcreated_at
FROM test t,
(SELECT #rowcreated_at := 0) r
ORDER BY t.created_at
) C -- add sort column for created_at
ON I.id = C.id
JOIN (
SELECT t.id, scomment,
#rowscomment := #rowscomment + 1 AS rscomment
FROM test t,
(SELECT #rowscomment := 0) r
ORDER BY t.scomment
) S -- add sort column for scomment
ON I.id = S.id
) T
ORDER BY CASE 1
WHEN 1 THEN rid
WHEN 2 THEN rcreated_at
WHEN 3 THEN rscomment
END

Answer 2

So after some more research and testing, I was able to find a way to do it, a little bit 'cleaner'.
SELECT id, created_at, scomment
FROM test
ORDER BY
CASE 1 WHEN 1 THEN id END ASC,
CASE 1 WHEN 2 THEN created_at END ASC,
CASE 1 WHEN 3 THEN scomment END ASC;
This will allow me to sort on a specific field correctly.
You could even add different directions by doing the following:
SELECT id, created_at, scomment
FROM test
ORDER BY
CASE p_order_by WHEN 1 THEN AND p_dir = 'asc' id END ASC,
CASE p_order_by WHEN 1 THEN AND p_dir = 'desc' id END DESC,
CASE p_order_by WHEN 2 THEN AND p_dir = 'asc' created_at END ASC,
CASE p_order_by WHEN 2 THEN AND p_dir = 'desc' created_at END DESC,
CASE p_order_by WHEN 3 THEN AND p_dir = 'asc' scomment END ASC,
CASE p_order_by WHEN 3 THEN AND p_dir = 'desc' scomment END DESC;
Where p_order_by is the number field you want to sort, and p_dir is the direction.