select語句：N的關係

Question

我有三個表：

用戶
用戶ID
FNAME
LNAME

集團
GROUPID
描述

USER_GROUP
usergroupid
userid
groupid

我需要獲取users表的名和姓。給出的是組描述。我怎麼能做到這一點？

Answer 1

SELECT a.Fname, 
     a.LName, 
     c.Description 
FROM [USER] a 
     INNER JOIN [USER_GROUP] b 
      ON a.userID = b.userID 
     INNER JOIN [GROUP] c 
      ON b.groupid = c.groupID 
WHERE c.Description = 'description_here' 

爲了進一步獲得更多的知識有關加入，請訪問以下鏈接：

• Visual Representation of SQL Joins

Answer 2

試試這個：

SELECT USER.* 
FROM USER 
    INNER JOIN USER_GROUP ON USER.userid = USER_GROUP.userid 
    INNER JOIN [GROUP] ON USER_[GROUP].groupid = [GROUP].groupid 
WHERE [GROUP].description = 'Blah blah' 

Answer 3

如何

Select FName, LName 
    From user u 
    Where Exists 
     (Select * From user_Group ug 
      join group g On g.GroupId = ug.groupId 
     Where ug.userId = u.UserId 
      anf g.description = @GroupDescription)