select jyh from (select jyh from jyb where zbh = 'A') as AA and (select jyh from jyb where zbh = 'B') as BB where AA.jyh = BB.jyh;
一共有三张表:图书表(tsb)(表里有:总编号(zbh)),借阅表(jyb)(表里有:总编号(zbh),借阅号(jyh)),读者表(dzb)(表里有:借阅号(jyh));
问题是: 查询图书总编号A和图书总编号为B的两本图书,被同一个借阅号借走
把from里的and 改成 逗号
select * from jyb j1,jyb j2 where j1.zbh='A' and j2.zbh='B' and j1.jyh = j2.jyh;