Question

我有一张表如下：

mysql> DESCRIBE student_lectures;
+------------------+----------+------+-----+---------+----------------+
| Field            | Type     | Null | Key | Default | Extra          |
+------------------+----------+------+-----+---------+----------------+
| id               | int(11)  | NO   | PRI | NULL    | auto_increment |
| course_module_id | int(11)  | YES  | MUL | NULL    |                |
| day              | int(11)  | YES  |     | NULL    |                |
| start            | datetime | YES  |     | NULL    |                |
| end              | datetime | YES  |     | NULL    |                |
| cancelled_at     | datetime | YES  |     | NULL    |                |
| lecture_type_id  | int(11)  | YES  |     | NULL    |                |
| lecture_id       | int(11)  | YES  |     | NULL    |                |
| student_id       | int(11)  | YES  |     | NULL    |                |
| created_at       | datetime | YES  |     | NULL    |                |
| updated_at       | datetime | YES  |     | NULL    |                |
+------------------+----------+------+-----+---------+----------------+

我基本上想要找到讲座没有发生的时间 - 所以为了做到这一点，我正在考虑将重叠讲座组合在一起（例如，上午9点到10点和上午10点到11点的讲座将是显示为上午9点至11点的演讲）。可能会有两个以上的讲座背靠背。

我现在有这个：

SELECT l.start, l2.end
FROM student_lectures l
LEFT JOIN student_lectures l2 ON ( l2.start = l.end )
WHERE l.student_id = 1 AND l.start >= '2010-04-26 09:00:00' AND l.end <= '2010-04-30 19:00:00' AND l2.end IS NOT NULL AND l2.end != l.start
GROUP BY l.start, l2.end
ORDER BY l.start, l2.start

返回：

+---------------------+---------------------+
| start               | end                 |
+---------------------+---------------------+
| 2010-04-26 09:00:00 | 2010-04-26 11:00:00 |
| 2010-04-26 10:00:00 | 2010-04-26 12:00:00 |
| 2010-04-26 10:00:00 | 2010-04-26 13:00:00 |
| 2010-04-26 13:15:00 | 2010-04-26 16:15:00 |
| 2010-04-26 14:15:00 | 2010-04-26 16:15:00 |
| 2010-04-26 15:15:00 | 2010-04-26 17:15:00 |
| 2010-04-26 16:15:00 | 2010-04-26 18:15:00 |
...etc...

我正在寻找的输出是：

+---------------------+---------------------+
| start               | end                 |
+---------------------+---------------------+
| 2010-04-26 09:00:00 | 2010-04-26 13:00:00 |
| 2010-04-26 13:15:00 | 2010-04-26 18:15:00 |

感谢任何帮助，谢谢！

Answer 1

这样的事情应该有效。

SELECT l2.start，l.end 来自student_lectures l LEFT JOIN student_lectures l2 ON l2.end 在l.start和l.end之间在哪里。开始 BETWEEN'2010-04-26 00:00:00'和'2010-04-26 23:59:59' GROUP BY l.start ORDER BY l.start

Answer 2

ax提出了迄今为止我见过的最佳答案 - 即http://explainextended.com/2009/06/13/flattening-timespans-mysql/

在MySQL中找到“免费”时间

2 个答案: