sql左链接三表关联

表A---------------------------------关联第一张表B-----------------------关联第二张表c

select * fomr 表名A　　left join 表B on 表A字段=表B的id 　　left join 表c 　on 表A字段=表c的id　

            表a--------------------------------表b----------------------------------表c

id        name                        id      bname    a_id                       id     cname   a_id

01          a1                          001          b1       01                        1         c1          01

02          a2                          002          b2       02                         2        c2           02

03          a3                                                                                     3        c3          03

04          a4                              

    select a.name,b.bname,c.cname       from a left join b on a.id=b.a_id    left join c on a.id=c.a_id  

结果：

name       bname       cname

a1                 b1               c1

a2                 b2               c2

a3                 null             c3

a4                 null             null

数据表随便弄的，大家将就一下。