Question

我们有以下输入：

ID,MONTH,AMOUNT
1,1,1.1
1,2,2.1
1,3,3.1

我们希望将其输出为：

ID,AMOUNT_JAN,AMOUNT_FEB,AMOUNT_MAR
1,1.1,2.1,3.1

到目前为止我们得到的查询：

SELECT ID,
CASE WHEN MONTH = '1' THEN AMOUNT END AS AMOUNT_JAN,
CASE WHEN MONTH = '2' THEN AMOUNT END AS AMOUNT_FEB,
CASE WHEN MONTH = '3' THEN AMOUNT END AS AMOUNT_MAR
FROM TEST2

只能生成如下输出：

ID,AMOUNT_JAN,AMOUNT_FEB,AMOUNT_MAR
1,1.1,NULL,NULL
1,NULL,2.1,NULL
1,NULL,NULL,3.1

任何一位大师能开导吗？

为方便起见，可以使用SQL Fiddle：

http://sqlfiddle.com/#!9/017d9c/3

Answer 1

添加enum和GROUP BY功能：

MAX

SQLFiddle Demo

Answer 2

您必须在GROUP BY子句中添加SELECT并使用条件聚合：

SELECT ID,
       MAX(CASE WHEN MONTH = '1' THEN AMOUNT END) AS AMOUNT_JAN,
       MAX(CASE WHEN MONTH = '2' THEN AMOUNT END) AS AMOUNT_FEB,
       MAX(CASE WHEN MONTH = '3' THEN AMOUNT END) AS AMOUNT_MAR
FROM TEST2
GROUP BY ID

Demo here

Answer 3

从技术上讲，你可以尝试：

SELECT
  ID
  , (SELECT AMOUNT FROM TEST2 WHERE ID = T_outer.ID AND MONTH = 1) AS AMOUNT_JAN
  , (SELECT AMOUNT FROM TEST2 WHERE ID = T_outer.ID AND MONTH = 2) AS AMOUNT_FEB
  , (SELECT AMOUNT FROM TEST2 WHERE ID = T_outer.ID AND MONTH = 3) AS AMOUNT_MAR
FROM TEST2 T_outer
GROUP BY ID
;

查看实际操作：SQL Fiddle。

请评论是否需要调整/进一步详细说明。

MySQL 5.6将行移动到列中（pivot函数）

3 个答案:

SQLFiddle Demo