hi there, hope in your help.

I've this query, I need this particular order because when the value of field `ISEG` is `GCL` the value of field `INTR` is null even if it is valued.

I've tried with syntax `order by case when` but without success...

Can you help me?
thank you.

Code:
mysql> SELECT
	CONCAT(
		DATE_FORMAT(DayOfEvent, '%d/%m/%Y'),
		' ',
		HourOfEvent
	) AS `Day_event`,
	CASE
WHEN (
	ii = 'CBT GDM, PS'
	OR NCLBTDIS = 1
) THEN
	'GCL'
WHEN (LENGTH(CCA) = 6 AND CTI = 'DV') THEN
	'SNG'
ELSE
	ISEG
END AS ISEG,
 INTR
FROM
	tbl_m20
ORDER BY
	INTR DESC,
	`Day_event` ASC;

+------------------+--------------+
| Day_event        | ISEG  | INTR |
+------------------+--------------+
| 05/03/2013 11:33 | ASL   |  204 |
| 05/03/2013 10:06 | GIG   |    0 |
| 05/03/2013 10:15 | GIC   |    0 |
| 05/03/2013 10:26 | SNG   |    0 |
| 05/03/2013 10:28 | SNG   |    0 |
| 05/03/2013 10:28 | SNG   |    0 |
| 05/03/2013 11:02 | SNG   |    0 |
| 05/03/2013 12:19 | GCL   |   28 |
| 05/03/2013 12:48 | SNG   |    0 |
| 05/03/2013 14:01 | SNG   |    0 |
| 05/03/2013 14:15 | GIG   |    0 |
| 05/03/2013 14:16 | SNG   |    0 |
| 05/03/2013 14:19 | GCL   |  598 |
| 05/03/2013 15:50 | GIG   |    0 |
| 05/03/2013 16:02 | GIC   |    0 |
| 05/03/2013 16:15 | GIG   |    0 |
| 05/03/2013 16:18 | SNG   |    0 |
| 05/03/2013 18:20 | GIG   |    0 |
| 05/03/2013 23:38 | GIG   |    0 |
+------------------+-------+------+
19 rows in set