Sql复合查询笔记

有一个product表：

查询每一列之和，按照category

select [category], sum([quantity]) Total from [testSql].[dbo].[product] group by [category]

查询最大的category：

select [category], oneTotal from (select [category], sum([quantity]) oneTotal from [testSql].[dbo].[product] group by [category]) T 
where oneTotal = (select max(oneTotal) from 
(select [category], sum([quantity]) oneTotal from [testSql].[dbo].[product] group by [category]) T)