Question

我有三张桌子

UserInfo（U-id，U-name）
技能（S-ID，S-NAME）和他们之间的桥牌表（因为他们有多对多关系）
UserSkill（U-ID，S-ID）

我想写一个查询来查找具有相同技能的用户例如，这是UserSkill表中的示例数据

U-id   S-id
1       1
1       2
1       7
2       1
2       6

所以结果会像这样

UserName1    UserName2   SkillName
A              B            Java

enter image description here

ad这是我的查询

{select ui.UserName,ui2.UserName,SkillName
  from 
  UserSkill us1 inner join UserSkill us2 
on us1.SkillID = us2.SkillID and us1.UserID <> us2.UserID
  inner join UsersINFO UI 
on ui.UserID = us1.UserID 
  inner join UsersINFO ui2 
on ui2.UserID = us2.UserID
  inner join Skill s 
on s.SkillID = us2.SkillID}

我想知道是否有人知道更好的方式来编写查询

Answer 1

您只需在末尾添加Where ui.UserName<ui2.UserName

select ui.UserName,ui2.UserName,SkillName
  from 
  UserSkill us1 inner join UserSkill us2 
on us1.SkillID = us2.SkillID and us1.UserID <> us2.UserID
  inner join UsersINFO UI 
on ui.UserID = us1.UserID 
  inner join UsersINFO ui2 
on ui2.UserID = us2.UserID
  inner join Skill s 
on s.SkillID = us2.SkillID
Where ui.UserName<ui2.UserName

输出

UserName    UserName    SkillName
A           B           Java

现场演示

http://sqlfiddle.com/#!18/64540/1

Answer 2

您查询的结果非常混乱。它报告A，B，java和B，A，java。

declare @J table (uid int, sid int, primary key (uid, sid));
insert into @J values 
       (1, 1)
     , (1, 2)
     , (1, 7)
     , (2, 1)
     , (2, 6)
     , (3, 1)
     , (3, 2);
declare @N table (id int primary key, name varchar(10));
insert into @N values 
       (1, 'bob')
     , (2, 'ted') 
     , (3, 'mac');
select j1.sid, n1.name, n2.name
from @J j1
join @J j2 
  on j2.sid = j1.sid 
 and j2.uid <> j1.uid
join @N n1 
  on n1.id = j1.uid
join @N n2 
  on n2.id = j2.uid
order by j1.sid, j1.uid, j2.uid;

sid         name       name
----------- ---------- ----------
1           bob        ted
1           bob        mac
1           ted        bob
1           ted        mac
1           mac        bob
1           mac        ted
2           bob        mac
2           mac        bob

即使您更换＆lt;＆gt;用＆gt;当你有超过2个具有相同技能时，它仍然是凌乱的。

select j1.sid, n1.name, n2.name
from @J j1
join @J j2 
  on j2.sid = j1.sid 
 and j2.uid > j1.uid
join @N n1 
  on n1.id = j1.uid
join @N n2 
  on n2.id = j2.uid
order by j1.sid, j1.uid, j2.uid;

sid         name       name
----------- ---------- ----------
1           bob        ted
1           bob        mac
1           ted        mac
2           bob        mac

我建议你不要成对报告

select * 
from ( select j1.sid, n1.name 
            , count(*) over (partition by j1.sid) as cnt
         from @J j1
         join @N n1 
           on n1.id = j1.uid 
     ) t
where t.cnt > 1
order by t.sid, t.name;

sid         name       cnt
----------- ---------- -----------
1           bob        3
1           mac        3
1           ted        3
2           bob        2
2           mac        2

Answer 3

以下内容返回具有相应技能的所有用户对以及该技能：

select ui.name, us2.name, s.s_name
from userskill us join
     userskill us2
     on us.sid = us2.sid join
     skills s
     on s.sid = us.sid join
     userinfo ui
     on ui.uid = us.uid join
     userinfo ui2
     on ui2.uid = us2.uid
where us.uid <> us2.uid;

用SQL查询查找具有相同技能的用户

3 个答案: