SQL - Where clause and distinct

本文关键字：and distinct clause Where SQL | 更新日期: 2023-09-27

我正在尝试使用PDO执行SQL查询，该查询将从两个不同的表中选择数据，并将它们匹配在一起：

$stmt = $dbh->prepare("
    select a.token, b.token, b.username, COUNT(DISTINCT a.token) adcount, COUNT(DISTINCT b.username WHERE a.token=b.token) clickcount
    from advertisements a, advertisement_clicks b
    where a.status='2' AND (a.clicks_left > 0 OR a.fixed ='1')
    AND b.token=a.token
    ");
    $stmt->bindParam(':userid', $userdata["id"]); 
    $stmt->execute();
    $s1=$stmt->fetch();

所以，上面的SQL不起作用。我正在尝试选择a.token与b.token匹配的记录的数量作为clickcount

我怎样才能做到这一点？

select 
a.token, b.token, b.username, COUNT(DISTINCT a.token) adcount, 
COUNT(DISTINCT b.username) clickcount
from advertisements a 
JOIN advertisement_clicks b ON b.token=a.token
where a.status='2' AND (a.clicks_left > 0 OR a.fixed ='1')

您已经在join表中了。您不需要在count中使用where子句。

以下是一个查询，用于选择a.token与b.token匹配的记录数量作为clickcount:

SELECT a.token, b.token, COUNT(a.token) clickcount
    FROM advertisements a
    JOIN advertisement_clicks b
    ON b.token=a.token
    WHERE a.status='2' AND (a.clicks_left > 0 OR a.fixed ='1')
    GROUP BY a.token;