聚合函数.sql

来自「简单的sql语句 数据与汇总。 高手多多指点。」· SQL 代码 · 共 41 行

use northwind
go

select top 5 with ties orderid,productid,quantity from [order details]
order by quantity desc
go

select sum(quantity) from [order details]
go

select * from [order details]
go

select count(*) from [order details]
go

select * from employees
go

select count(reportsto) from employees
go
--count(reportsto)将忽略null值

select count(*) from employees
go
--count(*)将计算所以行数，不会忽略null值


select 
num=count(*),
'avg salary'=avg(salary),
'low salary'=min(salary),
'avg age'=avg(age),
'low age'=min(age)
from employees
go

exec sp_help employees
go