请教sql语句问题

Question

请问一个如何写sql语句的问题三个表结构如下：user(username,age,....)cus(cusid,cusname)duty(username,cusid)如何写sql语句查询出user表中每个username对应的所有cusname？ 要遍历完username表哦...如下：（-代表空格）username-----cusname---a-----------aa,bb,cc---b--------------aa--- 这样写： select username,cusname from user,cus,duty where user.username=duty.username and user.cusid=duty.cusid结果不是如上显示形式哦...

Answer 1

NONONO...

 

select a.username ,c.cusname from user a

left join duty d on a.username=d.username

left join cus c on d.cusid=c.cusid

order by a.username

Answer 2

SELECT C.username,cusname
FROM cus A
INNER JOIN duty B ON A.cusid=B.cusid
INNER JOIN user C ON B.username=C.useranme

Answer 3

楼上正确