MySQL的獲取根據病情狀況

Question

中的行，我有以下以下

--------------------------------- 
| Id  | Value | Flag | 
--------------------------------- 
| 1  | 23  | 0 | 
--------------------------------- 
| 1  | 24  | 1 | 
--------------------------------- 
| 2  | 30  | 0 | 
--------------------------------- 

我需要查詢時，應取最後兩行。這裏的條件是IF兩行具有相同的Id，那麼輸出應該獲取flag = 1的行。如果對於Id只有一行，則應該獲取Flag = 0的行。因此，輸出爲給定的要求是

--------------------------------- 
| 1  | 24  | 1 | 
--------------------------------- 
| 2  | 30  | 0 | 

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Answer 1

其他答案看起來是正確的給我。這是一種不同的方法：

SELECT t1.* 
FROM 
    yourtable t1 LEFT JOIN yourtable t2 
    ON t1.Id = t2.Id AND t1.Flag=0 AND t2.Flag=1 
WHERE 
    t2.Id IS NULL 

請參閱小提琴here。

Answer 2

SELECT 
* 
FROM yourTable yt1 
WHERE Flag = (SELECT MAX(Flag) FROM yourTable yt2 WHERE yt1.Id = yt2.Id) 
GROUP BY Id 

Answer 3

我更喜歡uncorellated辦法...

SELECT x.* 
    FROM my_table x 
    JOIN 
    (SELECT id,MAX(flag) max_flag FROM my_table GROUP BY id) y 
    ON y.id = x.id 
    AND y.max_flag = x.flag;