我可以在SQL中选择一组平均值

Question

我可以根据SQL中的字段选择一组平均值吗？ 类似的东西：

SELECT 
    AVG(Salary WHERE department = 1) as AvgDept1,
    AVG(Salary WHERE title = 1) as AvgTitle1,
    AVG(TimeOnJob WHERE title = 1 and department = 1) as AvgTime1
FROM
    Employees

我理解这与带有GROUP BY的AVG类似，但我无法理解如何从中获取三个值。

Answer 1

那些看起来像三个单独的查询， 如果你想将它们捆绑成一个选择，你可以做类似的事情：

SELECT 
   (SELECT AVG(Salary) WHERE department = 1 FROM Employees) AS AvgDept1,
   (SELECT AVG(Salary)  WHERE title = 1 FROM Employees) AS AvgTitle1
   (select AVG(TimeOnJob) WHERE title = 1 and department = 1 FROM Employees) AS AvgTime1