條件MySQL查詢

Question

我有一個表的列：conditional1，conditional2，data。如果其中任何一行還包含conditional2 = value2，我需要返回所有行的條件1 =值1。我怎樣才能做到這一點？

編輯：我有些疑惑。

如果你有專欄

`conditional1 | conditional2 |數據

A | A | A

A | B | A`

我要回兩行，如果conditional1 = A和conditional2 = B

編輯2：目前仍然有些混亂。

這裏是另一個例子：

conditional1 | conditional2 |數據

1 | 1 | A

1 | 2 | B

2 | 1 | C

2 | 2 | D

如果conditional1 = 1且conditional2 = 1，則應該返回

1 | 1 | A

1 | 2 | B

如果conditional1 = 2且conditional2 = 1，則應該返回

2 | 1 | C

2 | 2 | d

如果conditional1 = 2和conditional2 = 2，則應該返回

2 | 1 | C

2 | 2 | D

如果conditional1 = 2且conditional2 = 3，則它不應該返回任何行。

Answer 1

select * 
from tbl A 
where conditional1 = 'A' 
and exists (
    select * from tbl B 
    where B.conditional1 = 'A' and B.conditional2 = 'B') 

或以上的MySQL版本適合

select * from tbl 
where conditional1 in 
(
    select conditional1 
    from tbl 
    where conditional1 = 'A' and conditional2 = 'B' 
) 

Answer 2

SELECT * FROM table 
    WHERE conditional1 = 'A' AND 1 IN 
     (SELECT 1 FROM table WHERE conditional1 = 'A' AND conditional2 = 'B' LIMIT 1) 

我想我終於明白了！