Question

如何选择＆amp;按天分组来自数据库的数据，但也包括没有条目的天数。在这种情况下，该值将为0.

如果不能使用MySQL，也可以使用PHP。

这是我目前所拥有的：

SELECT DATE_FORMAT(date, '%Y-%m-%d') AS the_date
     , COUNT(*) AS count 
  FROM table 
 WHERE date BETWEEN DATE_FORMAT('2016-11-28', '%Y-%m-%d') AND DATE_FORMAT('2016-12-05', '%Y-%m-%d') 
 GROUP 
    BY the_date

Answer 1

在PHP中添加缺少的日期可能更简单。在MySQL中，您需要从某个地方获取日期。通常，数据库具有包含此信息的“日历”表。如果你有一个，那么你想做的就是这样：

SELECT DATE_FORMAT(c.date, '%Y-%m-%d') AS the_date, COUNT(t.date) AS count 
FROM Calendar c LEFT JOIN
     table t
     ON c.date = t.date
WHERE c.date BETWEEN '2014-11-28' AND '2014-12-05' -- MySQL recognizes strings in the format of YYYY-MM-DD as dates when needed
GROUP BY the_date;

如果您没有这样的表，可以为查询创建一个表：

SELECT DATE_FORMAT(c.date, '%Y-%m-%d') AS the_date, COUNT(t.date) AS count 
FROM (SELECT date('2014-11-28') as date UNION ALL
      SELECT date('2014-11-29') as date UNION ALL
      SELECT date('2014-11-30') as date UNION ALL
      SELECT date('2014-12-01') as date UNION ALL
      SELECT date('2014-12-02') as date UNION ALL
      SELECT date('2014-12-03') as date UNION ALL
      SELECT date('2014-12-04') as date UNION ALL
      SELECT date('2014-12-05') as date 
     ) c LEFT JOIN
     table t
     ON c.date = t.date
GROUP BY the_date;

这适用于少数日期，但对于跨越数月或数年的范围而言效果不佳。

MySql每天选择和计算数据 - 包括空日期

1 个答案: