左联接呗~~left join 注意的是tag表要连两次,然后用别名区分! select * from content a left join tag b on a.c_ttype=b.id left join tag c on a.c_ttag=c.id left join user d on a.c_uid=d.id
select c.c_uid, u.u_name, c.c_ttype, t1.t_tag, c.c_ttag, t2.t_tag, c.c_content from content c inner join [user] u on c.c_uid=u.u_id inner join tag t1 on c.c_ttype=t1.t_id inner join tag t2 on c.c_ttag=t2.t_id
注意的是tag表要连两次,然后用别名区分!
select * from
content a left join tag b on a.c_ttype=b.id
left join tag c on a.c_ttag=c.id
left join user d on a.c_uid=d.id
u.u_name,
c.c_ttype,
t1.t_tag,
c.c_ttag,
t2.t_tag,
c.c_content
from content c
inner join [user] u
on c.c_uid=u.u_id
inner join tag t1
on c.c_ttype=t1.t_id
inner join tag t2
on c.c_ttag=t2.t_id