Question

我有一个有4列（id，发件人，收件人，状态）的朋友，我需要一个查询，它将联合发送者和接收者的发送者和接收者列结合在一起（重聚，我不知道英文单词）等于让我们说2。例如，表格如下所示

| sender | receiver |
|    2   |   10     |
|    2   |    8     |
|    2   |    9     |
|    6   |    2     |
|    7   |    3     |
|    10  |    3     |

在查询之后它将显示:(显示前3行因为sender = 2，然后第四行显示，因为接收器为2.其余行未显示）

| result |
|   10   |
|    8   |
|    9   |
|    6   |

Answer 1

你几乎拥有正确的关键字; UNION会让你做你想做的事。

SELECT `receiver` as `result` FROM `table` WHERE `sender` = 2
UNION
SELECT `sender` as `result` FROM `table` WHERE `receiver` = 2

Answer 2

select
case when sender = 2
then receiver
else sender
end
from friends
where sender = 2 or receiver = 2

Answer 3

这是您的查询，我希望对您有意义：

Select sender as result
from friends
where receiver = 2
union
Select receiver as result
from friends
where sender = 2

Answer 4

SELECT * 
FROM
    (SELECT sender as iResult
    FROM   friends
    WHERE  receiver = 2
         UNION
    SELECT receiver as result
    FROM friends
    WHERE sender = 2) c
 ORDER BY c.iResult DESC

mysql结合2列条件

4 个答案: