SQL在同一个表中组合两个查询而没有子查询

Question

表，Employee有EmployeeID，Salary列。 如何找到工资大于平均工资的EmployeeID？

使用子查询：

SELECT EmployeeID
FROM Employee
WHERE Salary > (SELECT AVG(Salary)
                 FROM Employee);

是否可以使用连接？ 还有其他方法吗？

Answer 1

以这种方式编写它似乎很愚蠢，但这里没有任何子查询：

SELECT a.EmployeeID
FROM Employee a
CROSS JOIN Employee b
GROUP BY a.EmployeeID, a.Salary
HAVING a.Salary > AVG(b.Salary)

Answer 2

/r/n

将平均工资计算移至FROM以计算一次。 BTW大多数现代数据库可以优化您的查询以计算一次。

Answer 3

SELECT * from 
(SELECT EmployeeID,salary AVG(salary) OVER() avg_salary FROM Employee) 
WHERE Salary >avg_salary

Answer 4

SELECT e.EmployeeID FROM Employee e
JOIN
(
 SELECT avg(Salary) as Salary FROM Employee
) e1
ON e.Salary > e1.Salary

Answer 5

Declare @AverageSalary as Money
Select @AverageSalary = AVG(Salary) From Employee
Select * from Employee Where Salary > @AverageSalary