如何在 MySql 中进行 SANDWICH 离开查询？

Question

你们中的许多人可能都知道三明治休假。但是如何在数据库级别实现对我来说有点困难。我有一个场景，如果员工休假 2 次，即在他们的周休假之前和之后，那么所有 3 天都应该标记为休假。 以下是我分享的基本要求。

HERE IS REQUIREMENT OF SANDWICH LEAVE

这是一些示例数据。我最终可能会想到用相应的期望结果来补充这一点。

CREATE TABLE IF NOT EXISTS `atnsystem` (
  `Emp_id` int unsigned NULL,
  `attendance_date` date NULL,
  `in_datetime` datetime NULL,
  `out_datetime` datetime NULL,
  `remark` varchar(100) NULL
) DEFAULT CHARSET=utf8;

INSERT INTO `atnsystem` (`Emp_id`, `attendance_date`, `remark`) VALUES
  ('66', '2020-02-17', 'LEAVE'),
  ('66', '2020-02-16', 'WEEK-OFF'),
  ('66', '2020-02-15', 'LEAVE');

这是 SQL_FIDDLE 链接table created in fiddler

我想如果 remark 像 LEAVE 、 WEEK-OFF 和 LEAVE 一样，那么 WEEK-OFF 也应该转换为 LEAVE。

插入什么并不重要，但是在使用 SELECT 查询时，如果它发现 YESTERDAY 为 LEAVE，TODAY 为 WEEK-OFF，然后在第二天再次为 LEAVE，那么 WEEK-OFF 日也应该被视为 LEAVE。我希望我能清楚地说明我的问题，并且非常感谢任何帮助。

Answer 1

解决此问题的一种方法是转换所有非休息日的内容，以便我们可以为每个休息日分配一个数字（下面查询中的块）。之后，我们可以知道每个块中的最小和最大日期，并且可以在主查询中使用一个简单的子查询来确定最小和最大日期之前和之后的备注是否为离开。 例如

+--------+-----------------+-------------+--------------+----------+
| Emp_id | attendance_date | in_datetime | out_datetime | remark   |
+--------+-----------------+-------------+--------------+----------+
|     66 | 2020-02-29      | NULL        | NULL         | week-off |
|     66 | 2020-02-28      | NULL        | NULL         | NULL     |
|     66 | 2020-02-27      | NULL        | NULL         | leave    |
|     66 | 2020-02-26      | NULL        | NULL         | week-off |
|     66 | 2020-02-25      | NULL        | NULL         | week-off |
|     66 | 2020-02-24      | NULL        | NULL         | NULL     |
|     66 | 2020-02-23      | NULL        | NULL         | leave    |
|     66 | 2020-02-22      | NULL        | NULL         | week-off |
|     66 | 2020-02-21      | NULL        | NULL         | week-off |
|     66 | 2020-02-20      | NULL        | NULL         | leave    |
|     66 | 2020-02-19      | NULL        | NULL         | NULL     |
|     66 | 2020-02-18      | NULL        | NULL         | leave    |
|     66 | 2020-02-17      | NULL        | NULL         | NULL     |
|     66 | 2020-02-16      | NULL        | NULL         | WEEK-OFF |
|     66 | 2020-02-15      | NULL        | NULL         | LEAVE    |
|     66 | 2020-02-14      | NULL        | NULL         | leave    |
+--------+-----------------+-------------+--------------+----------+
16 rows in set (0.00 sec)


select t.*, b.*,
         (select t1.remark 
         from t t1
         where t1.emp_id = t.emp_id and
                t1.attendance_date < b.mindt 
         order by t1.attendance_date desc limit 1) previous_remark,
         (select t1.remark 
         from t t1
         where t1.emp_id = t.emp_id and
                t1.attendance_date > b.maxdt 
         order by t1.attendance_date asc limit 1) next_remark   ,
         case
          when 
            (select t1.remark 
            from t t1
            where t1.emp_id = t.emp_id and
                t1.attendance_date < b.mindt 
            order by t1.attendance_date desc limit 1) = 'leave'
          AND
            (select t1.remark 
            from t t1
            where t1.emp_id = t.emp_id and
                t1.attendance_date > b.maxdt 
            order by t1.attendance_date asc limit 1) ='leave' THEN
             'leave'
          ELSE t.remark 
          END as final_remark    
from t
left join
(
select a.emp_id,a.bloc,min(a.attendance_date) mindt,max(a.attendance_date) maxdt
from
(
select s.*,
        if(newremark = 'p',0,If(newremark <> @p,@b:=@b+1,@b:=@b)) bloc,
        @p:=newremark p
from
(
select t.*,
        case when remark = 'week-off' then remark else 'p' end as newremark
from t
order by attendance_date asc
) s
cross join (select@b:=0,@p:='') b
order by attendance_date asc
) a
where bloc > 0
group by a.emp_id, a.bloc
) b
on b.emp_id = t.emp_id and t.attendance_date between b.mindt and b.maxdt
order by t.emp_id,t.attendance_date;

+--------+-----------------+-------------+--------------+----------+--------+------+------------+------------+-----------------+-------------+--------------+
| Emp_id | attendance_date | in_datetime | out_datetime | remark   | emp_id | bloc | mindt      | maxdt      | previous_remark | next_remark | final_remark |
+--------+-----------------+-------------+--------------+----------+--------+------+------------+------------+-----------------+-------------+--------------+
|     66 | 2020-02-14      | NULL        | NULL         | leave    |   NULL | NULL | NULL       | NULL       | NULL            | NULL        | leave        |
|     66 | 2020-02-15      | NULL        | NULL         | LEAVE    |   NULL | NULL | NULL       | NULL       | NULL            | NULL        | LEAVE        |
|     66 | 2020-02-16      | NULL        | NULL         | WEEK-OFF |     66 | 1    | 2020-02-16 | 2020-02-16 | LEAVE           | NULL        | WEEK-OFF     |
|     66 | 2020-02-17      | NULL        | NULL         | NULL     |   NULL | NULL | NULL       | NULL       | NULL            | NULL        | NULL         |
|     66 | 2020-02-18      | NULL        | NULL         | leave    |   NULL | NULL | NULL       | NULL       | NULL            | NULL        | leave        |
|     66 | 2020-02-19      | NULL        | NULL         | NULL     |   NULL | NULL | NULL       | NULL       | NULL            | NULL        | NULL         |
|     66 | 2020-02-20      | NULL        | NULL         | leave    |   NULL | NULL | NULL       | NULL       | NULL            | NULL        | leave        |
|     66 | 2020-02-21      | NULL        | NULL         | week-off |     66 | 2    | 2020-02-21 | 2020-02-22 | leave           | leave       | leave        |
|     66 | 2020-02-22      | NULL        | NULL         | week-off |     66 | 2    | 2020-02-21 | 2020-02-22 | leave           | leave       | leave        |
|     66 | 2020-02-23      | NULL        | NULL         | leave    |   NULL | NULL | NULL       | NULL       | NULL            | NULL        | leave        |
|     66 | 2020-02-24      | NULL        | NULL         | NULL     |   NULL | NULL | NULL       | NULL       | NULL            | NULL        | NULL         |
|     66 | 2020-02-25      | NULL        | NULL         | week-off |     66 | 3    | 2020-02-25 | 2020-02-26 | NULL            | leave       | week-off     |
|     66 | 2020-02-26      | NULL        | NULL         | week-off |     66 | 3    | 2020-02-25 | 2020-02-26 | NULL            | leave       | week-off     |
|     66 | 2020-02-27      | NULL        | NULL         | leave    |   NULL | NULL | NULL       | NULL       | NULL            | NULL        | leave        |
|     66 | 2020-02-28      | NULL        | NULL         | NULL     |   NULL | NULL | NULL       | NULL       | NULL            | NULL        | NULL         |
|     66 | 2020-02-29      | NULL        | NULL         | week-off |     66 | 4    | 2020-02-29 | 2020-02-29 | NULL            | NULL        | week-off     |
+--------+-----------------+-------------+--------------+----------+--------+------+------------+------------+-----------------+-------------+--------------+
16 rows in set (0.16 sec)

其中 t 是我的数据库中的表名。

请注意，您的数据必须是干净的，并且假设每个员工每天都有一个条目。我在你的输出中包含了比你需要的更多的列，这样你就可以看到发生了什么。