CREATE TABLE t1 (annee YEAR(4), mois INT(2) UNSIGNED ZEROFILL,
jour INT(2) UNSIGNED ZEROFILL);
INSERT INTO t1 VALUES(2000,1,1),(2000,1,20),(2000,1,30),(2000,2,2),
(2000,2,23),(2000,2,23);
SELECT annee,mois,BIT_COUNT(BIT_OR(1<<jour)) AS jours FROM t1
GROUP BY annee,mois;
Qui retourne :
+-------+-------+-------+
| annee | mois | jours |
+-------+-------+-------+
| 2000 | 01 | 3 |
| 2000 | 02 | 2 |
+-------+-------+-------+
|
