MySQL：查询中带有COUNT和groupby的WHERE子句？

对于我的广告使用的每个类别，我想显示广告的总数

我当前的查询如下所示：

SELECT
    categories_adverts.category,
    COUNT(adverts.id) AS numberOfAdverts
FROM adverts
LEFT JOIN categories_adverts
ON adverts.id_categories_adverts=categories_adverts.id
GROUP BY category ASC

我正在努力加入WHERE条款，该条款规定只有那些持续时间仍然有效的广告才会显示。我试图在广告和左加入之间加入以下条款…：

WHERE TIME_TO_SEC(timediff(now(),adverts.stamp_created))<=adverts.duration

所以整个查询都是这样的，但这不起作用：

SELECT
    categories_adverts.category,
    COUNT(adverts.id) AS numberOfAdverts
FROM adverts
WHERE TIME_TO_SEC(timediff(now(),adverts.stamp_created))<=adverts.duration
LEFT JOIN categories_adverts
ON adverts.id_categories_adverts=categories_adverts.id
GROUP BY category ASC

查询出了什么问题？

where子句位于联接之后

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WHERE子句应该在联接之后、分组和排序之前， 像这样：

SELECT
    categories_adverts.category,
    COUNT(adverts.id) AS numberOfAdverts
FROM adverts
LEFT JOIN categories_adverts
ON adverts.id_categories_adverts=categories_adverts.id
GROUP BY category ASC

选择 类别(u广告)类别,， COUNTadverts.id作为numberOfAdverts 从广告中 左联合广告 关于adverts.id\u categories\u adverts=categories\u adverts.id 时间到现在，创建了adverts.stamp