mysql - 选择表中只有一个值的行

Question

这是我的表的样子：

（前面不说了，colum2是字符串类型，不是整数，不好意思）

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

我只需要只有颜色=“红色”的行。
它必须返回“a”（“b”也包含值“Blue”）。

如何设置选择？谢谢并恭祝安康

Answer 1

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

• SQLFiddle Demo

here's another way,

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

• SQLFiddle Demo

UPDATE 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

如果该列可以采用 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'

或者如果它是整数，那么：

Select distinct Column1 from Table1 Where Column2=1

假设 Table1 是表名