是否可以封装sql-select结果? [英] Is it possible to encapsulate sql-select result?
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问题描述
简单SQL查询:
(选择 e.lastName as 名称,计数(o.orderid) as numOrd 来自
员工e join 订单o e.employeeid = o.employeeid
group by e.lastName)
和结果
Buchanan 42
Callahan 104
Davolio 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 名称,计数(o.orderid) as numOrd 来自
员工e join 订单o on e.employeeid = o.employeeid
group by e.lastName )
之后写这样的东西,这将是输出:
选择 AVG(qr.numOrd)来自 queryResult qr
是否可以不创建任何新表?
解决方案
您要求的方式无法在SQL中运行。你必须选择:
1.声明一个表变量并将第一个选择的结果插入其中,而不是在第二个选择中使用
2.使用第一个在from部分中选择 - select * from(从表中选择字段)
答案是CTE的
http://technet.microsoft.com/en-us/library/ms190766(v = SQL.105)的.aspx 一> [ ^
Simple SQL query:
(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)
and result
Buchanan 42
Callahan 104
Davolio 123
Dodsworth 43
My question is how to achieve in SQL something like that:
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)
and after that to write something like this, which will be the output:
select AVG(qr.numOrd) from queryResult qr
Is it possible without creating any new tables?
解决方案
The way you ask for can't work in SQL. You have to options:
1. Declare a table variable and insert the results of the first select into it, than use it in the second select
2. Use the first select in the from part - select * from (select field from table)
The answer was CTE's
http://technet.microsoft.com/en-us/library/ms190766(v=sql.105).aspx[^]
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