MySQL如何有条件地计数和求和

Question

加入两个表后我得到MySQL的结果如下：-

        ID              ||    Category      ||       Cost       ||
========================||==================||==================|| 
AMWP/ABC/2016-17/1      ||      1           ||      123.88      ||
AMWP/CDF/2016-17/2      ||      2           ||      222.99      ||
AMWP/GHI/2016-17/3      ||      3           ||      133.90      ||
AMWP/ABC/2017-18/1      ||      1           ||      100.10      ||
AMWP/CDF/2017-18/2      ||      2           ||      200.20      ||
AMWP/GHI/2017-18/3      ||      3           ||      100.00      ||

我想根据类别和每个类别的计数和成本总和仅在 ID 具有类似于 ABC/CDF/GHI 之一和财政年度类似于 2016-17/2017-18 的条件下提取摘要

Answer 1

我得到了我想要的方式。在以下 SQL 中，只要 Condition 为 True，我将使用 Sum 而不是 Count 到 Add 1 to TotWks。另外，只要条件为True，我只需Adding Cost Field 到TotCost。

SELECT
Category,
SUM(if(ID LIKE '%2017-18%' AND ID like ‘%/ABC/%, 1, 0)) AS `TotWks`,
SUM(if(ID LIKE '%2017-18%' AND ID like ‘%/ABC/%, `amwplist`.`Cost`, 0)) AS `TotCost`
FROM  <main_Table>
LEFT OUTER JOIN <join_Table> ON <main_Table.ID> = <join_Table. ID> 
GROUP BY <main_Table.ID>

如果我省略了GROUP BY 子句，那么我将在TotWks 和TotCost 下总计。

感谢大家的帮助。

Answer 2

    select category, sum(Cost)
        from your_tables
        where 
        ( ID like ‘%/ABC/% or ID like ‘%/CDF%/’ or ID like ‘%/GHI/%’ )
        and 
        ( ID like ‘%/2016-17/%’ or ID like ‘%/2017-18/%’ )
        and <joining condition>
        group by category;