select SalesPersonID,OrderDate,Max(TotalDue) as MaximumTotalSales
from [Sales].[SalesOrderHeader]
# 从 [Sales].[SalesOrderHeader]中选出SalesPersonID,OrderDate，并求出TotalDue的最大值，作为新的变量MaximumTotalSales
where SalesPersonID is not null and OrderData>='2007/1/1'
#符合该条件的才能被筛选出来
group by SalesPersonID,OrderDate
#分组
having Max(TotalDue)>150000
#限定范围
order by OrderDate desc
#降序排列
'% mountain%' 表示含有'mountain'的字符串
'_ountain%'表示不确定ountain前面的字符是什么
用法：
where f.description like '%mountain%'
查找含有'mountain'的字符串
