摘要： 透视转换：use tempdb;if object_id('dbo.Orders', 'U') is not null drop table dbo.Orders;create table dbo.Orders( orderid int not null, orderdate date not null, empid int not null, custid varchar(5) not null, aty int not null, constraint pk_Orders primary key(... 阅读全文

摘要： {TODO:} 阅读全文

摘要： 1.派生表(derived table)select YEAR(orderdate) as orderyear, COUNT(distinct custid) as numcustsfrom Sales.Ordersgroup by YEAR(orderdate);内联别名select orderyear, COUNT(distinct custid)from (select YEAR(orderdate)as orderyear, custid from Sales.Orders) as Dgroup by orderyear外部命名select orderyear, COUNT(disti 阅读全文

摘要： 简单子查询select * from (select custid, companyname from Sales.Customers where country = N'USA') as USACusts关联子查询select custid, orderid, orderdate, empidfrom Sales.Orders as o1where orderid = (select max(o2.orderid) from Sales.Orders as o2 where o2.custid = o1.custid)select orderid, custid, val.. 阅读全文

摘要： {TODO:} 阅读全文