mysql - 将 WHERE 子句添加到 Left Join 的一个表中？

Question

我加入 Sites 和 History 并选择不在 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
        "); 

问题是我想将 WHERE UID = $uid 添加到表 History 中，所以我只连接具有所述 UID 的行。

我想做这样的事情:

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

这可能吗？我该怎么做？

Answer 1

您可以将其添加到 JOIN 子句中:

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

或 WHERE 子句:

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

注意:您应该使用适当的表名作为前缀。我会的，但你没有具体说明。