Mysql SQL：连接到两个表，然后使用sum（）和count（）

如果我有两张桌子：

学校：

school_id | class_id | school_location
-------------------------------------------
400             50               Arizona

工作人员：

staff_id | forename | school_id | wage
------------------------------------------
1           Peter          400         5000

我怎样才能得到产出，在学校工作的员工人数和每所学校的工资

例如：

school_id | numberofstaff | salary
---------------------------------------
400 |           1         | 5000

我知道我应该这样加入表格：

SELECT school_id 
FROM school 
INNER JOIN staff
ON school.school_id = staff.school_id

但是，我不确定如何执行查询的其余部分

SELECT numberofstaff COUNT(numberofstaff) from staff
GROUP BY school_id
Union all 
select 'SUM' numberofstaff, COUNT(numberofstaff)
FROM staff

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这应该给我我的学校id，以及每个学校id的员工人数。

一旦你加入两个表，你就可以计算员工人数并计算每个学校的所有工资：

SELECT sc.school_id, 
   COUNT(*) as numberofstaff,
   SUM(st.wage) as salary
FROM school sc
INNER JOIN staff st
ON sc.school_id = st.school_id
GROUP BY sc.school_id

这样试试

SELECT COUNT(staff.numberofstaff) as numberofstaff , school.school_id as school_id FROM school 
INNER JOIN staff
ON school.school_id = staff.school_id
GROUP BY school.school_id;

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那么这个select查询是否会在我的join语句下面呢？不，这个查询就是要执行的全部内容。啊，现在它有了意义。谢谢