没有嵌套的计数 select：这可能吗？

Question

数据库：

Department  Position             Points
    A        Manager               50
    A        Supervisor            10
    A        Supervisor            10
    A        Staff                 2
    A        Staff                 2
    B        Manager               40
    B        SuperVisor            8
    B        Staff                 2
    B        Staff                 2
    B        Staff                 2

想要的查询结果：

Dept  Manager Count  Supervisor Count  Staff Count    Staff Total Pts   

A        1                  2              2                 4
B        1                  1              3                 4

如果不使用带计数的嵌套 select 是否可以获得所需的查询结果？

我们有一个使用嵌套计数的类似于此的特定存储过程，我们希望使其更简单并执行 better/faster

Answer 1

使用Conditional Aggregate只计算特定数据

Select Department,
       count(case when Position = 'Manager' then 1 END) as Manager,
       count(case when Position = 'Supervisor' then 1 END) as Supervisor,
       count(case when Position = 'Staff' then 1 END) as Staff
From yourtable
Group by Department

如果您正在使用 Sql Server，请使用此

SELECT Department,
       Manager,
       Supervisor,
       Staff
FROM   Yourtable
       PIVOT (Count(Position)
             FOR Position IN (Manager,Supervisor,Staff))pv

Answer 2

使用条件 SUM:

SELECT Department,
       SUM(CASE WHEN Position = 'Manager' THEN 1 END) as Manager,
       SUM(CASE WHEN Position = 'Supervisor' THEN 1 END) as Supervisor,
       SUM(CASE WHEN Position = 'Staff' THEN 1 END) as Staff
FROM yourtable
GROUP BY Department

Answer 3

或者您可以使用 PIVOT 运算符：

select Detartment, Manager, Supervisor, Staff
from yourtable
pivot (count(Position) for Position in (Manager, Supervisor, Staff)) Result

没有嵌套的计数 select：这可能吗？

Count without nested select: is this possible?

sql

count

sql-optimization