入门基础条件

Question

我有两个关系

Author (authorId, authorName, country) 

PrizeWinner (mAuthId, fAuthId, year) 

其中的元组的列表：

fk(mAuthId) -> authorId of Author 
fk(fAuthId) -> authorId of Author 

获得者表包含谁赢得了最佳作者奖对给定雌雄配对的Id年。

我们需要列出所有获奖作者对，当雄（mAuthID）和女作家（fAuthId）是来自同一个国家

任何帮助或线索，在此将得到高度赞赏。 谢谢。

Answer 1

SELECT male.*, female.* 
FROM 
    PrizeWinner p 
     INNER JOIN Author male ON male.authorId = p.mAuthId 
     INNER JOIN Author female ON female.authorId = p.fmAuthId 
WHERE 
    male.country = female.country 

关于你的评论，试试这个：

SELECT DISTINCT all.authorName, all.country 
FROM 
    PrizeWinner p 
     INNER JOIN Author male ON male.authorId = p.mAuthId 
     INNER JOIN Author female ON female.authorId = p.fmAuthId 
     INNER JOIN Author all ON all.authorId = male.authorId OR all.authorId = female.authorId 
WHERE 
    male.country = female.country