FROM Customer a LEFT JOIN OrderMaster b ON a.CustomerNo =b.CustomerNo ORDER BY a.CustomerNo ,orderSum 结果：
(21) 查找16M DRAM的销售情况，要求显示相应的销售员的姓名、性别，销售日期、销售数量和金额，其中性别用“男”、“女”表示。 命令：
select employeeName , case sex when 'F' then '女' when 'M' then '男' end as 性别, orderDate ,quantity ,sum(quantity *price )as 金额 from Employee a,OrderMaster b,OrderDetail c
where employeeNo =salerNo and b.orderNo =c.orderNo and ProductNo in (select ProductNo from Product where ProductName ='16M DRAM')
group by employeeName ,sex , orderDate ,quantity 结果：
(22) 查找每个人的销售记录，要求显示销售员的编号、姓名、性别、商品名称、数量、单价、金额和销售日期。 命令：
select employeeNo ,employeeName ,sex ,ProductName ,quantity ,price ,sum(quantity *price ) as ordersum, orderDate
from Employee a,OrderMaster b,OrderDetail c,Product d
where employeeNo =salerNo and b.orderNo =c.orderNo and c.ProductNo =d.ProductNo group by employeeNo ,employeeName ,sex ,ProductName ,quantity ,price , orderDate 结果：