合并计数主题、评论和最后评论日期论坛 sql

Question

Im developing a forum-like website I want to put the next information within a div

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

Here I count the number of posts

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

   $sql->execute();

Here I count the number of comments

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

   $sql->execute();

Here I find the last comment date

   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();

My greatest probles is How should I merge all those three sql sentences and 3 pdo execution in one single sql statement (single pdo execution)?

Answer 1

You can join and aggregate. Consider:

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