Question

我有一张约会表，其中包含我想要每周自动复制的日期和学生ID。我想运行一个查询，该查询检测每个约会是否提前一周都有自己的副本，因此原始数据为：

PupilID   Date
1         10th May
2         16th May

查询后，

PupilID   Date
1         10th May
2         16th May
1         17th May
2         23rd May

我试图使用以下但没有运气。建议将不胜感激。我已经有代码完成这项工作，但它变得非常慢。

INSERT timetable (pupil_id,date) SELECT timetable.pupil_id AS pupil_id2,DATE_ADD(timetable.date,INTERVAL 14 DAY) AS date2 FROM timetable WHERE  NOT EXISTS pupil_id2=timetable.pupil_id AND date2=timetable.date;

Answer 1

检查是否有未来的预约是否足够？

试一试：

insert into timetable (pupil_id,date)
select t.pupil_id, DATE_ADD(t.date, INTERVAL 14 DAY)
from timetable t 
where not exists (select 1 from timetable
                         where pupil_id = t.pupil_id
                         and date > t.date)

您可以更改最后一个条款以专门检查提前14天：

where not exists (select 1 from timetable
                         where pupil_id = t.pupil_id
                         and date = DATE_ADD(t.date, INTERVAL 14 DAY))

我推荐第一个查询。

在MySQL中有条件地重复记录

1 个答案: