我有下表,其中我正在尝试SUM,如果type ='printer',但是,我不想计算重复的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 |
| 101 | 3 |
+-----------+--------------------------------+
预期结果:
+-----------+--------------------------------+
| client_id | SUM(IF(type = 'printer', 1,0)) |
+-----------+--------------------------------+
| 102 | 0 |
| 100 | 0 |
| 101 | 1 |
+-----------+--------------------------------+
答案 0 :(得分:8)
使用:
SELECT x.client_id,
COUNT(DISTINCT y.type)
FROM FOO x
LEFT JOIN FOO y ON y.client_id = x.client_id
AND y.type = 'printer'
GROUP BY x.client
如果您不需要查看零计数的行:
SELECT client_id,
COUNT(DISTINCT type)
FROM FOO
WHERE type = 'printer'
GROUP BY type, client_id;
答案 1 :(得分:7)
有三行,类型为printer
。 Sum
将它们全部添加,然后返回3.
如果您希望1
看到包含打印机的行,而0
则为max
,请尝试使用sum
代替MAX(IF(type = 'printer', 1,0))
^^^
:
SELECT client_id
, (
select count(*)
from FOO as f2
where f1.client_id = f2.client_id
and type = 'Printer'
)
FROM FOO as f1
GROUP BY
client_id
编辑:要计算不同打印机的数量,可以使用子查询:
{{1}}
答案 2 :(得分:1)
SELECT client_id, if( `type` = 'printer', 1, 0 )
FROM foo
GROUP BY TYPE , client_id
答案 3 :(得分:0)
SELECT distinct client_id,
(IF(type = 'printer', 1,0))
FROM FOO
(我猜:我不熟悉IF(..))