SQL或比较只是一个结果

Question

我试着使依赖于结果的SQL查询只返回一个专栏中，我有下表：

day1  | day2  | day3 
------------------------------------- 
2013-02-25 | 2013-02-26 | 2013-02-27 

---

所以我只想要一个查询返回一天行，

SELECT * FROM days WHERE day1 = '2013-02-25' or day2 = '2013-02-25' or day = '2013-02-25' 

我想下一个，只有行谁有价值。

day  | 
------------ 
2013-02-25 | 

Answer 1

试试这个：

SELECT day1 AS TheDay FROM days WHERE day1 = '2013-02-25' 
UNION 
SELECT day2   FROM days WHERE day2 = '2013-02-25' 
UNION 
SELECT day3   FROM days WHERE day3 = '2013-02-25'