Question

我正在开发类似论坛的网站我想将下一个信息放入div

 Category: Cars
 Topics: 27  Comments:5436
 Last Comment: 01.04.2020 //php formated

我在这里计算帖子数

   SELECT * 
   FROM posts as p
   WHERE p.category= :category 

   $sql->execute();

我在这里计算评论数

   SELECT * 
   FROM comments as c
   LEFT JOIN posts as p ON c.id_post = p.id_post
   WHERE p.category= :category 

   $sql->execute();

在这里我找到了最后的评论日期

   SELECT max(c.date) as maxdate
   FROM comments as c
   LEFT JOIN posts as p ON c.id_post = p.id_post
   WHERE p.category= :category 
   GROUP BY c.id_comment

   $sql->execute();

我最大的问题是如何将所有这三个sql语句和3个pdo执行合并到一个sql语句中（单个pdo执行）？

Answer 1

您可以加入并聚集。考虑：

select 
    p.category,
    count(distinct p.id_posts) no_posts,
    count(c.id_post)           no_comments,
    max(c.date)                date_last_comment
from posts p
left join comments c on c.id_post = p.id_post
where p.category= :category 
group by p.category

合并主题，评论和最后评论日期论坛SQL的数量

1 个答案: