按次數（*）子查詢

Question

全新的子查詢，我試圖從表showcase通過他們的評論數（按降序）並不知道如何訂購帖子。

SELECT * 
FROM showcase 
ORDER BY 
    (select count(*) 
    from comments) 
DESC 

Answer 1

我們需要沿着使用組數：

select s.postId, count(c.commentid) as comments 
from showcase s join comment c on s.postId = c.postId 
group by s.postId 
order by comments desc 

Answer 2

如果你只需要身份證，group by和每個組

select showcase.id 
from showcase left join comments on comments.item_id = showcase.id 
group by showcase.id 
order by count(showcase.id) desc 

Answer 3

，你可以指望行嘗試一個更適合查詢的連接查詢。

SELECT `showcase`.*, count(`comments`.`item_id`) as item_id FROM `showcase` 
LEFT JOIN `comments` 
ON `showcase`.`id`, `comments`.`item_id` 
ORDER BY item_id DESC 

讓我知道是工作或沒有。