Question

我有多行需要不同的concat函数。该表看起来像这样

A B C D E F
-----------
1 H E Y
2 T H E E R
3 W O R D L

我想添加另一个单词concatenated，我已经这样做了

SELECT *, CONCAT(B, C, D) AS G FROM table

显然它会返回

A B C D E F G
-------------
1 H E Y     HEY
2 T H E E R THE
3 W O R D L WOR

有没有办法让结果

A B C D E F G
-------------
1 H E Y     HEY
2 T H E E R THERE
3 W O R D L WORLD

答案解决了简化问题：

如何将这3个选择语句合并为1？

SELECT *, CONCAT(C, B, E, D, F) AS G FROM table WHERE A = 1; 
SELECT *, CONCAT(G, C, D, B, E, F) AS G FROM table WHERE A = 2; 
SELECT *, CONCAT(D, E, F, C, B) AS G FROM table WHERE A = 3;

Answer 1

SELECT *,
    CASE A 
        WHEN 1 THEN CONCAT(C, B, E, D, F)
        WHEN 2 THEN CONCAT(C, D, B, E, F)
        WHEN 3 THEN CONCAT(D, E, F, C, B)
    END AS G
FROM table
WHERE A IN (1, 2, 3)

或者您可以使用UNION组合单独的查询：

SELECT *, CONCAT(C, B, E, D, F) AS G
FROM table
WHERE A = 1
UNION
SELECT *, CONCAT(C, D, B, E, F) AS G
FROM table
WHERE A = 2
UNION
SELECT *, CONCAT(D, E, F, C, B) AS G
FROM table
WHERE A = 3

我可以为选择查询中的每一行设置自定义CONCAT（）吗？ MySQL的

1 个答案: