Question

我有两张桌子

oc2_visits（fields：id_ad）
oc2_ads（字段：已发布）

我需要通过对id_ad进行分组来计算访问次数，这是有效的，但我还要求前9个结果的发布时间不超过25天。

这是我目前的查询：

SELECT count(v.id_ad) AS visits,
       v.id_ad,
       a.published
FROM oc2_visits AS v,
     oc2_ads AS a
WHERE DATE(a.published) >= DATE_SUB(NOW(), INTERVAL 25 DAY)
GROUP BY v.id_ad
ORDER BY visits DESC LIMIT 0,9

但是当我尝试在phpmyadmin中输入查询时，它会崩溃。

我做错了什么？

Answer 1

大概你问题的根源是两个表之间的笛卡尔积。简单规则：永远不要在from子句中使用逗号。始终使用明确的join语法。

我想你想要的查询看起来像这样：

SELECT count(v.id_ad) AS visits, v.id_ad, a.published
FROM oc2_visits v join
     oc2_ads a
     ON v.id_ad = a.id_ad
WHERE DATE(a.published) >= DATE_SUB(NOW(), INTERVAL 25 DAY)
GROUP BY v.id_ad
ORDER BY visits DESC
LIMIT 0, 9;

Answer 2

我认为您在与DATE比较时忘记将DATE_SUB(NOW(), INTERVAL 25 DAY)解析为DATE。希望它能运作。

SELECT count(v.id_ad) AS visits,
       v.id_ad,
       a.published
FROM oc2_visits AS v,
     oc2_ads AS a
WHERE DATE(a.published) >= DATE(DATE_SUB(NOW(), INTERVAL 25 DAY))
GROUP BY v.id_ad
ORDER BY visits DESC LIMIT 0,9

从具有另一个表中的Where的表中选择计数

2 个答案: