目标 - 列出每个部门的男性平均工资和女性平均工资。显示部门名称和编号。
select AVG(salary) as 'Avg salary for men'
From [Enterprise].[dbo].[Employee]JOIN [Enterprise].[dbo].[Department]
ON Employee.EMPNO = Department.deptNo
where SEX = 'm'
还在学习连接，不确定我是否需要在这里进行外部连接？我如何让它按部门列出平均值？
我会假设你打算加入deptNo。
SELECT Department.Name, AVG(salary) as 'Avg salary for men'
FROM [Enterprise].[dbo].[Employee]
JOIN [Enterprise].[dbo].[Department]
ON Employee.deptNo= Department.deptNo
WHERE SEX = 'm'
GROUP BY Department.Name
这将显示男性每个部门的平均值。您可以对女性执行相同的操作，并使用 将她们包含在查询中UNION。或添加到您的GROUP BY性别，并WHERE完全删除该子句。
Y的列表GROUP B通常会匹配列表中的非聚合列SELECT。在这种情况下，它只是 Department.Name。
好吧，首先，您似乎使用Employee了JOIN. 也就是说，您的查询应该是这样的：
SELECT D.deptNo,
D.deptName,
AVG(CASE WHEN E.SEX = 'm' THEN salary END) [Avg salary for men],
AVG(CASE WHEN E.SEX = 'f' THEN salary END) [Avg salary for women]
FROM [Enterprise].[dbo].[Employee] E
INNER JOIN [Enterprise].[dbo].[Department] D
ON E.deptNO = D.deptNo -- use the right column from Employee here
GROUP BY D.deptNo,
D.deptName
SQL OUTER JOIN 子句是 SQL JOIN 子句的一种变体，它允许 SELECT 语句访问多个表。JOIN 子句控制表的链接方式。它是 SQL FROM 子句的限定符。因此，您需要 OUTER JOIN 在您的情况下。如果需要，您可以访问该链接以获取更多信息。
要将输出作为部门平均值的列表，只需将其添加到查询的末尾：
ORDER BY Department.deptNo
没有人解释过某些部门可能没有男性或女性的事实。
SELECT D.deptNo,
D.deptName,
Coalesce(AVG(CASE WHEN E.SEX = 'm' THEN salary END), 0) [Avg salary for men],
Coalesce(AVG(CASE WHEN E.SEX = 'f' THEN salary END, 0)) [Avg salary for women]
FROM [Enterprise].[dbo].[Department] D
LEFT JOIN [Enterprise].[dbo].[Employee] E
ON E.deptNO = D.deptNo -- use the right column from Employee here
GROUP BY D.deptNo,
D.deptName
SELECT Employee.EMPNO, Department.Name, SEX, AVG(salary) as [Avg salary]
FROM [Enterprise].[dbo].[Employee]JOIN [Enterprise].[dbo].[Department]
ON Employee.EMPNO = Department.deptNo
GROUP BY Employee.EMPNO, Department.Name, SEX
这将为您获取数据，您可以从这里随意格式化。
Query1 :
SELECT Table1.*, Table2.[Roll no],Table2.Address,Table2.City
FROM (Table1 right JOIN Table2 ON Table1.[roll no] = Table2.[roll no] and Table1.[status] = Table2.[status])
where Table1.Status="New" or Table2.status="New"
UNION SELECT Table1.*,Table2.[roll no], table2.Address,table2.City
FROM (Table1 left JOIN Table2 ON Table1.[roll no] = Table2.[roll no] and Table1.[status] = Table2.[status])
where Table1.Status="New" or Table2.status="New";
Qury2:
SELECT Table3.*,table4.[roll no],Table4.Sports_id,Table4.Name
FROM (Table3 right JOIN Table4 ON Table3.[roll no] = Table4.[roll no] and Table3.[status] = Table4.[status])
where Table3.Status="New" or Table4.status="New"
UNION SELECT Table3.*,table4.[roll no],Table4.Sports_id,Table4.Name
FROM (Table3 left JOIN Table4 ON Table3.[roll no] = Table4.[roll no] and Table3.[status] = Table4.[status])
where Table3.Status="New" or Table4.status="New";
Query3:
SELECT *
FROM (Query2 right JOIN Query3 ON Query2.[Table1.roll no] = Query3.[table3.roll no])
UNION SELECT *
FROM (Query2 left JOIN Query3 ON Query2.[Table1.roll no] = Query3.[table3.roll no]);
Query4:
SELECT Query4.* INTO Final_table
FROM Query4;
Query5:
UPDATE Final_Table SET Query2_Status = "New"
WHERE Query2_Status is null or Query2_status="";
正如所指出的，您的加入条件没有意义，您正在将员工编号加入部门编号，这将不匹配（或将，但不会实现您想要的逻辑）。
SELECT
d.name
, AVG(e_man.salary) avg_man
, AVG(e_woman.salary) avg_woman
FROM department d
LEFT OUTER JOIN employee e_man ON e_man.deptNo = d.deptNo AND e_man.sex = 'm'
LEFT OUTER JOIN employee e_woman ON e_woman.deptNo = d.deptNo AND e_woman.sex = 'f'
GROUP BY d.name
在这里，您加入两次，一次加入男性行，一次加入女性行，并根据它们计算平均值。如果没有任何男性/女性，则使用外部连接。
注意：我的查询将为每个部门返回一行，男性和女性的平均值为 2 列。替代解决方案是为每个部门返回 0-2 行，每个性别有单独的行，并列出每行/性别的相关薪水。
编辑：人们似乎非常不满意的替代子查询解决方案。根据我的经验，有时子查询是正确的答案，有时连接是正确的答案，只要不牺牲性能，您通常会使用最适合您的逻辑目标/表示的任何一个。无论如何，您正在使用的 RDBMS 的优化器通常会重写它。与往常一样，最好检查计划并查看发生了什么。
SELECT
d.name
, (
SELECT AVG(e1.salary)
FROM employee e1
WHERE e1.sex = 'm'
AND e1.deptNo = d.deptNo
) avg_man
, (
SELECT AVG(e2.salary)
FROM employee e2
WHERE e2.sex = 'f'
AND e2.deptNo = d.deptNo
) avg_woman
FROM department d