Question

简单SQL查询：

(select e.lastName as Name, count(o.orderid) as numOrd from
Employees e join Orders o on e.employeeid=o.employeeid
group by e.lastName)

和结果

布坎南42
卡拉汉104
达沃利奥123
Dodsworth 43

我的问题是如何在SQL中实现类似的东西：

let queryResult = 
(select e.lastName as Name, count(o.orderid) as numOrd from
Employees e join Orders o on e.employeeid=o.employeeid
group by e.lastName)

然后写下这样的东西，这将是输出：

select AVG(qr.numOrd) from queryResult qr

是否可以不创建任何新表？

Answer 1

是的，但为什么不是这样的：

select count(o.orderid) / count (distinct e.employeeid) AvgNumOrder
  from orders

派生表，CTE，子查询，临时表，表变量都按照您的要求执行，但不需要任何操作。

Answer 2

您可能想要使用a Common Table Expression (CTE)。

Answer 3

查看SQL Server Views

您可以将视图定义为

create view queryResult as
select e.lastName as Name, count(o.orderid) as numOrd from
Employees e join Orders o on e.employeeid=o.employeeid
group by e.lastName;

是否可以封装sql-select结果？

3 个答案: