一道題來對mysql的鏈接查詢複習

題目如上，下面是我按照上面的表字段本身建的表

car

customer

employee

sale

下面是對第四問的的解答，用的是mysql 的鏈接查詢，可能方法有點麻煩。

個人想法很簡單，這個查詢針對多個表，我就把須要查詢的結果一個個的先作簡單查詢，最後再進行組合。

第一步：從sale和car表中查出每一個員工的銷售額：

SELECT sale.EMPnum,SUM((sale.CARnum*car.Cprice)) AS money  FROM sale,car WHERE sale.CARnum=car.Cid GROUP BY EMPnum;#從sale和car表中查出每一個員工的

第二步：查詢每一個員工的銷售數量：

SELECT EMPnum,COUNT(EMPnum) AS num FROM sale GROUP BY EMPnum;#查詢每一個員工的銷售數量　　

第三步：查詢員工的名稱：　　

SELECT Eid,Ename FROM Employee;#查詢員工的名字

第四步：將第一步和第二步的結果作爲此次查詢的表，查詢每一個員工的銷售額和銷售數量：

 

SELECT t1.EMPnum,t1.money,t2.num FROM (SELECT sale.EMPnum,SUM((sale.CARnum*car.Cprice)) AS money  FROM sale,car WHERE sale.CARnum=car.Cid GROUP BY EMPnum) AS t1 ,(SELECT EMPnum,COUNT(EMPnum) AS num FROM sale GROUP BY EMPnum) AS t2 WHERE t1.EMPnum=t2.EMPnum;

 

　第五步：將第四步的結果和第三步的結果作爲這步的查詢表，查詢最後的結果

SELECT t3.EMPnum,t3.money,t3.num,t4.Ename FROM (SELECT t1.EMPnum,t1.money,t2.num FROM (SELECT sale.EMPnum,SUM((sale.CARnum*car.Cprice)) AS money  FROM sale,car WHERE sale.CARnum=car.Cid GROUP BY EMPnum) AS t1 ,(SELECT EMPnum,COUNT(EMPnum) AS num FROM sale GROUP BY EMPnum) AS t2 WHERE t1.EMPnum=t2.EMPnum) AS t3,(SELECT Eid,Ename FROM Employee) AS t4 WHERE t3.EMPnum=t4.Eid;