我试了好几个小时想出一个查询，但我什至不知道这是否有可能将不同行的信息集中在一起

Question

我有一个样本table存储信息如下：两个子系统是mini1和mini2

System	Date	Sub System	Count
primary	2022-05-11	mini1	103
secondary	2022-05-11	mini2	100
secondary	2022-05-11	mini1	10
backup	2022-05-11	mini2	95
backup	2022-05-11	mini1	11
primary	2022-05-11	mini2	15
primary	2022-04-01	mini1	0
secondary	22022-04-01	mini2	0
secondary	2022-04-01	mini1	100
backup	2022-04-01	mini2	0
backup	2022-04-01	mini1	110
primary	2022-04-01	mini2	0

我想以如下格式获取每个系统的最新信息，其中只考虑最新日期。

System	Latest Date	mini1 Count	mini 2 Count
primary	2022-05-11	103	15
secondary	2022-05-11	10	100
backup	2022-05-11	11	95

这可以通过 sql 实现吗？

Answer 1

做一个GROUP BY。使用case表达式做条件聚合.

select System,
       max(Date) LatestDate,
       sum(case when SubSystem = 'mini1' then count else 0 end) Mini1Count,
       sum(case when SubSystem = 'mini2' then count else 0 end) Mini2Count
from tablename
group by System

我试了好几个小时想出一个查询，但我什至不知道这是否有可能将不同行的信息集中在一起

I tried for many hours to come up with a query but I don't even know if this is possible to have information from different rows in one

mysql

sql