我有一个数据库,有以下两个表
帖子
|post_id| text |post_date(time_stamp)|
喜欢:
| like_id | likee (1 or -1) | post_id | like_date (time_stamp) |
我正在尝试恢复所有在过去一个小时内喜欢的帖子,并按在过去一个小时内收到多少喜欢的帖子排序。
我尝试了以下查询,该查询返回了过去一小时内所有受欢迎的帖子,但我还无法确定如何按每个帖子ID的likee总和排序。
SELECT * FROM posts
INNER JOIN likes ON posts.post_id = likes.post_id
WHERE TIMESTAMPDIFF(HOUR,like_time,NOW())< 1 AND likee= 1
有什么方法可以通过修改查询来实现它吗?
最佳答案
首先计算最后一小时的喜欢(或积极的喜欢):
SELECT post_id,
SUM( likee ) as total_likes,
SUM( CASE WHEN likee = 1 THEN 1 ELSE 0 END ) as total_positive_likes
FROM likes
WHERE like_date >= DATE_SUB(NOW(),INTERVAL 1 HOUR)
GROUP BY post_id;
注意,您没有更改字段
like_date
,而是从NOW()
创建一个常量,这样就可以使用index。现在你加入了你的帖子
SELECT p.*, l.total_likes
FROM Post p
JOIN ( SELECT post_id,
SUM( likee ) as total_likes,
SUM( CASE WHEN likee = 1 THEN 1 ELSE 0 END ) as total_positive_likes
FROM likes
WHERE like_date >= DATE_SUB(NOW(),INTERVAL 1 HOUR)
GROUP BY post_id
) L
ON p.post_id = l.post_id
ORDER BY l.total_likes DESC