FROM Customer a LEFT OUTER JOIN OrderMaster b ON a.CustomerNO =b.CustomerNo WHERE year(orderDate )='2008' and month(orderDate )='2' 结果：
(18) 查找定单金额高于8000的所有客户编号。 命令：
SELECT CustomerNo
FROM OrderDetail as a,OrderMaster as b WHERE a.orderNo =b.orderNo GROUP BY CustomerNo
HAVING sum(quantity *price )>8000 结果：
(19) 显示每种商品的销售金额总和，并依销售金额由大到小输出。 命令：
SELECT productNo ,sum(price *quantity ) 销售金额 FROM OrderDetail GROUP BY productNo
ORDER BY 销售金额 desc 结果：
(20) 查找销售金额最大的客户名称和总货款。 命令：
SELECT top 1 CustomerName ,max(总货款) 总货款 FROM (SELECT CustomerNo ,sum(orderSum ) 总货款