查询以从多个表中获取信息 [英] querry to get information from multiple tables

问题描述

我有4个表名

T1 {umr，uid，mid}
T2 {mr，mid，rid}
T3 {rf，rid，fid}
T4 {fid，fname}

给定的值是
uid
中

并收到的是
fname

i have 4 tables names

T1{umr, uid, mid}
T2{mr, mid, rid}
T3{rf, rid, fid}
T4{fid, fname}

given values are
uid
mid

and to receive is
fname

推荐答案

可以使用简单的连接来实现，如下所示:

It can be achieved using simple joins, like as follows:

select fname from T4 
inner join T3 on T4.fid = T3.fid 
inner join  T2 on T3.rid = T2.rid 
inner join T1 on T2.mid = T1.mid

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