如何使用left-join爲這種類型的問題編寫mySQL？

Question

如何使用左連接構造mySQL查詢以解決此問題？

Feed Table 
-id 
-lastpost_id (The id of the user from USER TABLE who last posted) 
-firstpost_id (The id of the user from USER TABLE who first posted) 

User Table 
-id 
-name 

我希望得到一個表像

Result 
-id 
-lastpost_id 
-lastpost_name 
-firstpost_id 
-firstpost_name 

Answer 1

select *, a.name as lastpost_name, b.name as firstpost_name from Feed f 
     left join user a on f.lastpost_id=a.id 
     left join user b on f.firstpost_id=b.id 

訣竅是左連接，然後別名表爲a或b。通過這種方式，您可以對同一個表進行多次連接。