mysql - 使用 join 和 group by 进行复杂的选择查询

Question

我有两个 mysql 表，我想做一个选择查询:我的目标是计算某个订户从当前时间开始的过去 7 天的积分。第一个表显示每个订阅者点击内容 ID 1、2 或 3 中的某个内容的时间。他可能在某一天没有内容点击，因此他这一天不会获得积分。

表格如这些图片所示。 我的选择查询不完整:

   SELECT SUM( points ) AS POINT, DAY FROM
 (SELECT content_hits.content_id, COUNT( * ) * points AS points, 
DATE_FORMAT( hit_time,  "%d-%m-%Y" ) AS  DAY 
FROM content_hits JOIN content 
WHERE content_hits.content_id = content.content_id AND subscriber_id =1
 AND DATE_FORMAT( hit_time,  "%Y-%m-%d" ) > ( CURDATE( ) - INTERVAL 7 DAY )
 GROUP BY content_hits.content_id, DAY) AS tm 
GROUP BY DAY 
ORDER BY DAY DESC

结果如下图所示:

我预计以下日期的计数为零:17-7-2102、16-7-2012、15-7-2012、14-7-2012 和 12-7-2012。有什么建议吗？

Answer 1

需要创建日历表以在左连接中使用

CREATE TABLE ints (i INTEGER);
INSERT INTO ints VALUES (0), (1), (2), (3), (4), (5), (6), (7), (8), (9);

将日历表左连接到您的查询。

 SELECT cal.date,COALESCE(a.point,0) as point
 FROM (
    SELECT DATE_FORMAT(CURDATE() + INTERVAL a.i * 10 - b.i DAY,"%Y-%m-%d") as date
    FROM ints a JOIN ints b
    ORDER BY a.i * 10 - b.i
 ) cal LEFT JOIN 
 (SELECT SUM( points ) AS POINT, DAY FROM
  (SELECT content_hits.content_id, COUNT( * ) * points AS points, 
    DATE_FORMAT( hit_time,  "%Y-%m-%d" ) AS  DAY 
   FROM content_hits JOIN content 
   WHERE content_hits.content_id = content.content_id AND subscriber_id =1
     AND DATE_FORMAT( hit_time,  "%Y-%m-%d" ) > ( CURDATE( ) - INTERVAL 7 DAY )
   GROUP BY content_hits.content_id, DAY) AS tm 
   GROUP BY DAY 
 )a
 ON cal.date = a.day
 WHERE cal.date BETWEEN CURDATE( ) - INTERVAL 7 DAY AND CURDATE()
 ORDER BY cal.date desc;

SQL DEMO在这里。