PHP：从MySQL选择多个count（id）作为一个查询

Question

我需要在一个查询中优化以下代码：

        $query = 'select count(id) as featured_ads from #___properties  WHERE featured = 1 and approved =1';
    $db->setQuery($query);
    $featured_ads = intval($db->loadResult());


    $query = 'select count(id) as wait_ads from #___properties  WHERE approved =0 and canceled<>"1" ';
    $db->setQuery($query);
    $wait_ads = intval($db->loadResult());


    $query = 'select count(id) as total_users from #__sresuad WHERE gid = 18 ';
    $db->setQuery($query);
    $total_users = intval($db->loadResult());

我该怎么办？

Answer 1

您想在一次查询中返回所有计数吗？ 解决此问题的一种简单方法是让所有SELECT都为外部SELECT定义字段：

SELECT
    (select count(id) from #___properties  WHERE featured = 1 and approved =1) AS featured_ads,
    (select count(id) from #___properties  WHERE approved =0 and canceled<>"1") AS wait_ads,
    (select count(id) from #__sresuad WHERE gid = 18) AS total_users

正如Lodder在其评论中所建议的那样，手工编写SQL查询容易出错和降低安全性，因此，如果可能，您可能要避免这样做。