select b.songname , c.username , a.content from 留言内容 a left outer join 歌曲表 b on a.songid=b.songid left outer join 用户表 c on a.userid=c.userid where a.state=1
select b.songname , c.username , a.content from 留言内容 a left outer join 歌曲表 b on a.songid=b.songid left outer join 用户表 c on a.userid=c.userid where a.state=1用户表的数据都取不出来
create table tab_content (content_id int, userid int, songid int, state int, content varchar(200), unique(content_id) ) insert into tab_content values(1,1,1,1,'good') insert into tab_content values(2,2,1,1,'good too') insert into tab_content values(3,1,2,1,'good not') insert into tab_content values(4,2,2,1,'great') insert into tab_content values(5,2,1,0,'ok') insert into tab_content values(6,1,2,0,'aaaa') insert into tab_content values(7,1,2,0,'ffffffffffff') --------------------------------------------- create table tab_song ( songid int, songname varchar(50), unique(songid) ) insert into tab_song values(1,'小城故事') insert into tab_song values(2,'雨一直下') ---------------------------------------------- create table tab_user ( userid int, username varchar(50), unique(userid) ) insert into tab_user values(1,'张三') insert into tab_user values(2,'李四') ---------------------------------------------- select b.songname , c.username , a.content from tab_content a left outer join tab_song b on a.songid=b.songid left outer join tab_user c on a.userid=c.userid where a.state=1 --结果 songname username content 小城故事 张三 good 小城故事 李四 good too 雨一直下 张三 good not 雨一直下 李四 great-- 楼主,绝对没有问题 -- 一定是你搞错了 -- 不信你试验一下
from 留言内容 a
left outer join 歌曲表 b on a.songid=b.songid
left outer join 用户表 c on a.userid=c.userid
where a.state=1
from 留言内容 a
left outer join 歌曲表 b on a.songid=b.songid
left outer join 用户表 c on a.userid=c.userid
where a.state=1用户表的数据都取不出来
(content_id int,
userid int,
songid int,
state int,
content varchar(200),
unique(content_id)
)
insert into tab_content values(1,1,1,1,'good')
insert into tab_content values(2,2,1,1,'good too')
insert into tab_content values(3,1,2,1,'good not')
insert into tab_content values(4,2,2,1,'great')
insert into tab_content values(5,2,1,0,'ok')
insert into tab_content values(6,1,2,0,'aaaa')
insert into tab_content values(7,1,2,0,'ffffffffffff')
---------------------------------------------
create table tab_song
( songid int,
songname varchar(50),
unique(songid)
)
insert into tab_song values(1,'小城故事')
insert into tab_song values(2,'雨一直下')
----------------------------------------------
create table tab_user
( userid int,
username varchar(50),
unique(userid)
)
insert into tab_user values(1,'张三')
insert into tab_user values(2,'李四')
----------------------------------------------
select b.songname , c.username , a.content
from tab_content a
left outer join tab_song b on a.songid=b.songid
left outer join tab_user c on a.userid=c.userid
where a.state=1
--结果
songname username content
小城故事 张三 good
小城故事 李四 good too
雨一直下 张三 good not
雨一直下 李四 great-- 楼主,绝对没有问题
-- 一定是你搞错了
-- 不信你试验一下
顺便说一下
lw1a2 的回答有问题
内联 会出现错误