將WHERE子句添加到Left Join上的一個表中？

Question

我加入Sites與History並選擇不在History中的行。

$data = mysql_query(" 
     select * from Sites 
     left join History 
     on Sites.URL = History.URL 
     where History.URL is null 
     order by Karma 
     "); 

的問題是，我想補充WHERE UID = $uid錶的歷史，所以我只參加行與所述UID。

我想要做這樣的事情：

select * from Sites 
    left join History where UID = $uid 
    on Sites.URL = History.URL 
    where History.URL is null 
    order by Karma 

這可能嗎？我怎樣才能做到這一點？

Answer 1

您可以將它添加到JOIN條款：

select * from Sites 
left join History ON UID = $uid 
AND Sites.URL = History.URL 
where History.URL is null 
order by Karma 

或WHERE條款：

select * from Sites 
left join History 
AND Sites.URL = History.URL 
where History.URL is null 
and UID = $uid 
order by Karma 

注意：您應該用適當的表名加前綴。我會但你沒有指定。

Answer 2

嘗試用not exists條款：

select * from Sites 
where not exists (
    select * from History 
    where UID = $uid 
    and Sites.URL = History.URL) 
order by Karma 

Answer 3

是這樣說的：

select * from Sites s 
Where Not Exists 
    (Select * From History 
    Where URL Is Null 
     And uid = $uid) 
order by Karma