入門基礎條件

Question

我有兩個關係

Author (authorId, authorName, country) 

PrizeWinner (mAuthId, fAuthId, year) 

其中的元組的列表：

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

獲得者表包含誰贏得了最佳作者獎對給定雌雄配對的Id年。

我們需要列出所有獲獎作者對，當雄（mAuthID）和女作家（fAuthId）是來自同一個國家

任何幫助或線索，在此將得到高度讚賞。 謝謝。

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 

關於你的評論，試試這個：

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