Question

这是我的表格：

（我之前没有说过，colum2是字符串类型，不是整数，对不起）

╔══════╦═══════╗
║ USER ║ COLOR ║
╠══════╬═══════╣
║ a    ║ Red   ║
║ b    ║ Blue  ║
║ c    ║ Blue  ║
║ b    ║ Red   ║
║ a    ║ Red   ║
║ c    ║ White ║
╚══════╩═══════╝

我只需要独占 color =“Red”的行。
它必须返回“a”（“b”也包含值“Blue”）。

如何设置选择？谢谢和问候

Answer 1

SELECT  column1
FROM    TableName
GROUP   BY Column1
HAVING  COUNT(DISTINCT column2) = 1
        AND MAX(column2) = 1

SQLFiddle Demo

这是另一种方式，

SELECT  column1
FROM    TableName
GROUP   BY Column1
HAVING  MAX(column2) = MIN(column2) AND
        MAX(column2) = 1

SQLFiddle Demo

更新1

SELECT  user
FROM    TableName
GROUP   BY user
HAVING  SUM(color = 'red') = COUNT(*)

SQLFiddle Demo

Answer 2

更有效的方法是比较min和max值：

select column1
from t
group by column1
having min(column2) = max(column2) and min(column2) = 1

如果列可以采用NULL值，则还需要排除这些值：

select column1
from t
group by column1
having min(column2) = max(column2) and min(column2) = 1 and count(column2) = count(*)

Answer 3

Select distinct Column1 from Table1 Where Column2='1'

如果它是整数，那么：

Select distinct Column1 from Table1 Where Column2=1

假设Table1是表名

选择一个表中只有一个值的行

3 个答案: