MSSQL表查询问题

Question

有人可以告诉我如何获得在两个表之间使用MSSQL的正确数据结果,如下所示

**Person_Table**          **Departemnt_Table**
===========                 ================
person_id                   depatment_id
age                         department name 
gender                         
department_id

而且,我希望得到以下列的结果:

Department Names, 
Number under 20 aged Males in each department, 
number of under 20 aged Females in each department, 
total number of Males in each department, 
total number of Females in each department and, 
Total number of Persons in each department

示例结果应该如下所示

DepartmentName|(Under20)Male|(Under20)Female|Total(M)| Total(F)| Grand Total
Department1   |    1        |  3            |  1     |  3      |   4  
Department2   |    3        |  1            |  15    |  1      |   16
Department3   |    0        |  0            |  0     |  0      |   0

Answer 1

您需要使用聚合函数来使用GROUP By子句.

SELECT DT.DepartmentName,
        SUM(CASE WHEN PT.age < 20 AND PT.gender='MALE' THEN 1 ELSE 0 END) As [(Under20)Male]
       ,SUM(CASE WHEN PT.age < 20 AND PT.gender='FEMALE' THEN 1 ELSE 0 END) As [(Under20)FeMale],
       ,SUM(CASE WHEN PT.gender='MALE' THEN 1 ELSE 0 END) As [Total(M)]
       ,SUM(CASE WHEN PT.gender='FEMALE' THEN 1 ELSE 0 END) As [Total(F)]
       ,COUNT(*) As [Grand Total]   
FROM Departemnt_Table DT
INNER JOIN Person_Table PT ON DT.depatment_id = PT.depatment_id
GROUP BY DT.DepartmentName