小编Jos*_*osh的帖子

我有下表,其中我尝试SUM,如果type ='printer',但是,我不想重复client_ids.所以我希望这样的事情:

+------+-----------+-----------+
| k_id | client_id | type      |
+------+-----------+-----------+
|    1 |       100 | pc        | 
|    2 |       101 | printer   | 
|    3 |       101 | printer   | 
|    4 |       101 | printer   | 
|    5 |       102 | cellphone | 
+------+-----------+-----------+

查询:

  SELECT client_id, 
         SUM(IF(type = 'printer', 1,0)) 
    FROM FOO 
GROUP BY type, client_id;

结果:

+-----------+--------------------------------+
| client_id | SUM(IF(type = 'printer', 1,0)) |
+-----------+--------------------------------+
|       102 |                              0 | 
|       100 |                              0 …