Enkelt SQL til at hente forskellige oplysninger fra forskellige tabeller

Hvis nogle data måske ikke findes i en af ​​tabellerne, i stedet for at bruge INNER JOIN du skal bruge LEFT JOIN :

SELECT content.loc,content.id,content.title,
   -- USE function COALSESCE will show 0 if there are no 
   -- related records in table voting_count
    COALESCE(voting_count.up, 0) as votes_up,  
    COALSESCE(voting_count.down, 0) as voted_down
FROM content LEFT JOIN voting_count 
    ON content.id = voting_count.unique_content_id 
ORDER BY content.id DESC