在 Mysql 中对不同条件的行求和

Question

原表很大，我将其简化：

我的表：

CONDITION SIZE 
1          10
9          10
9          10
1          20
9          20
1          20
1          30

查询类似于

SELECT
  CASE WHEN CONDITION=1 THEN 'OK' ELSE 'BAD' END AS Status,
  SUM (CASE WHEN SIZE=10 THEN 1 ELSE 0 END) AS Small,
  SUM (CASE WHEN SIZE=20 THEN 1 ELSE 0 END) AS Medium,
  SUM (CASE WHEN SIZE=30 THEN 1 ELSE 0 END) AS Large,
FROM mytable GROUP BY Status

那么我们就有了这个结果

Status    Small    Medium    Large
OK         1         2         1
BAD        2         1         0

获取的正确代码是什么：

Status    Small    Medium    Large
OK         1         2         1
BAD        2         1         0
TOTAL      3         3         1   

Answer 1

您可以像这样将WITH ROLLUP 子句添加到您的GROUP BY 条件中：

SELECT
  CASE WHEN CONDITION=1 THEN 'OK' ELSE 'BAD' END AS Status,
  SUM (CASE WHEN SIZE=10 THEN 1 ELSE 0 END) AS Small,
  SUM (CASE WHEN SIZE=20 THEN 1 ELSE 0 END) AS Medium,
  SUM (CASE WHEN SIZE=30 THEN 1 ELSE 0 END) AS Large,
FROM mytable
GROUP BY Status WITH ROLLUP

这将产生如下结果集：

Status    Small    Medium    Large
OK         1         2         1
BAD        2         1         0
[NULL]     3         3         1 

您需要了解“状态”列中没有任何Total 值的行为。相反，Status 列将具有 NULL 值，指示这是进行汇总的位置。

有关更多信息，您可以在此处阅读文档：http://dev.mysql.com/doc/refman/5.6/en/group-by-modifiers.html

Answer 2

如果我理解正确，您需要在总查询中联合，因为您不能同时以不同的方式聚合。

SELECT
  CASE WHEN CONDITION=1 THEN 'OK' ELSE 'BAD' END AS Status,
  SUM (CASE WHEN SIZE=10 THEN 1 ELSE 0 END) AS Small,
  SUM (CASE WHEN SIZE=20 THEN 1 ELSE 0 END) AS Medium,
  SUM (CASE WHEN SIZE=30 THEN 1 ELSE 0 END) AS Large,
FROM mytable GROUP BY Status

UNION

SELECT
  'Total' AS Status,
  SUM (CASE WHEN SIZE=10 THEN 1 ELSE 0 END) AS Small,
  SUM (CASE WHEN SIZE=20 THEN 1 ELSE 0 END) AS Medium,
  SUM (CASE WHEN SIZE=30 THEN 1 ELSE 0 END) AS Large,
FROM mytable