SQL或比較只是一個結果

Question

我試着使依賴於結果的SQL查詢只返回一個專欄中，我有下表：

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

---

所以我只想要一個查詢返回一天行，

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

我想下一個，只有行誰有價值。

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

Answer 1

試試這個：

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'