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三表关联 lEFt join

inner join(等值连接) 只返回两个表中联结字段相等的行 left join(左联接) 返回包括左表中的所有记录和右表中联结字段相等的记录 right join(右联接) 返回包括右表中的所有记录和左表中联结字段相等的记录 INNER JOIN 语法: INNER JOIN 连接两...

比如有三张表,student,teacher , project : 第一种方法:select * from student,teacher,project where student.id=teacher.sid and student.id=project.sid; 第二种:select * from student inner join teacher on student.id=teacher.sid i...

大哥你以B为主表查埃。以A去LEFT JOIN肯定会多的! select b.sheetid,b.productid,c.name,b.number,a.companyid,a.ordertimefrom orderitem b left join order a on b.sheetid = a.sheetid left join product c on b.productid = c.productid

select a.id,a.name, sum(b.value) value, (select sum(c.value) from C c where a.id=c.aid) value2 from A a left join B b on a.id=b.aidgroup by a.id,a.nameorder by a.id,a.name

例如三个表A,B,C的关联: 如果B的二级数据或C的二级数据不一定存在,用以下语句: delete A,B,C from A left join B on B.id_b=A.id left join C on C.id_c=A.id where (B.id_b=A.id) or (C.id_c=A.id); 删除3个表都存在的关联数据: delete A,B...

可以写两个join $result = $room->join('left join r_hospital on r_department.hospital_id=r_hospital.id ')->join(' doctor on doctor.id = xx.id')->where($condition)->select();

首先,你得确认,3个表中哪个表需要显示全部数据(假设为shop)。然后,用左关联始终把shop放前面连接就可以了。比如: select a.*,b.Fitemname as username,c.Fitemname as Typename from shop a left outer join user b on a.FuserID=b.Fitemid...

SELECT * FROM tb_brand c left join (SELECT * FROM tb_product a,tb_info b WHERE a.itemname = b.itemname AND a.catname ='手机') d on d.brand = c.brand; 没试,但写完后感觉只会比你的更慢。 我认为,想提速最好不要三表联查,让前两个表...

select * from A left join B on (A.id = B.uid) left join C on (A.id = C.tid) group by A.kk

是否是你正在编辑那个表的结构的同时来做查询啊?是否是你已打开了2个或更多个Access,而且其中有1个正在编辑那个表的结构呢?

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