大侠帮忙看一下。sql查询出来结果是树结构
表1
A.id A.NameA
1 a
表2
B.id B.NameB B.Aid
1 b 1
2 b2 1
表3
C.id C.NameC C.Bid
1 c 1
表结构就是这样，我想查询出来的结构是：
NameA NameB NameC
a null null
a b null
a b c
a b2 null SQL
[解决办法]
create table table1
(id int,nameA varchar(50))
create table table2
(id int,nameB varchar(50),aid int)
create table table3
(id int,nameC varchar(50),bid int)
insert into table1
select 1,'a'
insert into table2
select 1,'b',1 union all
select 2,'b2',1
insert into table3
select 1,'c',1
select a.nameA,b.nameB,c.nameC
from table1 a
left join table2 b on a.nameA=b.nameB
left join table3 c on a.nameA=c.nameC
union all
select a.nameA,b.nameB,c.nameC
from table1 a
left join table2 b on a.id=b.aid
left join table3 c on a.nameA=c.nameC
union all
select a.nameA,c.nameB,c.nameC
from table1 a
left join
(
select a.nameB,b.nameC,a.id
from table2 a
left join table3 b on a.id=b.bid
)c on a.id=c.id
