如何選擇不同的列作爲列表？

Question

我有一個數據庫是這樣的：

column1 column2 column3 
15  21  19 
17  12  13 
15  24  14 

現在，我想每一個號碼的名單如下：

x value 
1 15 
2 21 
3 19 
4 17 
5 12 
... 

謝謝！

Answer 1

試試這個：

SELECT (@auto:=@auto+1) AS num, val 
FROM (SELECT column1 AS val 
     FROM tableA 
     UNION 
     SELECT column2 AS val 
     FROM tableA 
     UNION 
     SELECT column3 AS val 
     FROM tableA 
    ) AS A, (SELECT @auto:=0) AS B