[英]How to make triggers for delete and adding with if statement MySQL?
有两个表的 Queue (appointment_id, actual_time) Queue_Summary (date, doctor_id, num_of_patients)
第一个是所有队列,第二个是每个医生在某个日期的队列数。 我需要构建一个更新 num_of_patients 的触发器,每次在队列中添加队列时,我都需要在该日期添加到医生 num_of_patients。 拆的时候也是。
我刚刚计算了给定医生 ID 和日期的队列数量,并将其分为两个触发器。 但我唯一的问题是我在哪里放置 if 语句来检查这个日期是否在 Queue_Summary 上,如果没有则添加它。
(PS - 我不是 100% 的,因为我的数据库有点关闭并且有很多问题,如果在 thoes 声明中有任何问题,我会更乐意知道)
delimiter //
CREATE TRIGGER update_queue_summary
AFTER DELETE ON queue
FOR EACH ROW
BEGIN
update queue_summary as qs set num_of_patient = (
select count(appointment_id)
from queue as q join appointment as a on appointment_id
where a.doctor_id=qs.doctor_id and date(qs.actual_time)=date(qs.date())
group by appointment_id
) where doctor_id=qs.doctor_id and date(qs.actual_time)=date(qs.date());
END;//
delimiter ;
delimiter //
CREATE TRIGGER update_queue_summary
AFTER insert ON queue
FOR EACH ROW
BEGIN
update queue_summary as qs set num_of_patient = (
select count(appointment_id)
from queue as q join appointment as a on appointment_id
where a.doctor_id=qs.doctor_id and date(qs.actual_time)=date(qs.date())
group by appointment_id
) where doctor_id=qs.doctor_id and date(qs.actual_time)=date(qs.date());
END;//
delimiter ;
您应该在触发器中执行存在测试。 例如
drop table if exists queue,queue_summary;
create table queue (appointment_id int auto_increment primary key, doctor_id int,actual_time datetime);
create table Queue_Summary (date date, doctor_id int, num_of_patients int);
delimiter $$
create trigger ut after insert on queue
for each row
begin
if not exists (select 1 from queue_summary where date = date(new.actual_time) and doctor_id = new.doctor_id) then
insert into queue_summary values(date(new.actual_time),new.doctor_id,1);
else
update queue_summary
set num_of_patients = num_of_patients + 1
where date = date(new.actual_time) and doctor_id = new.doctor_id;
end if;
end $$
delimiter ;
insert into queue (doctor_id,actual_time) values(1,'2020-05-03 09:00'),(1,'2020-05-03 09:30');
select * from queue;
select * from queue_summary;
MariaDB [sandbox]> select * from queue;
+----------------+-----------+---------------------+
| appointment_id | doctor_id | actual_time |
+----------------+-----------+---------------------+
| 1 | 1 | 2020-05-03 09:00:00 |
| 2 | 1 | 2020-05-03 09:30:00 |
+----------------+-----------+---------------------+
2 rows in set (0.001 sec)
MariaDB [sandbox]> select * from queue_summary;
+------------+-----------+-----------------+
| date | doctor_id | num_of_patients |
+------------+-----------+-----------------+
| 2020-05-03 | 1 | 2 |
+------------+-----------+-----------------+
1 row in set (0.001 sec)
删除触发器类似但更简单
delimiter $$
create trigger dt after delete on queue
for each row
begin
if exists (select 1 from queue_summary where date = date(OLD.actual_time) and doctor_id = old.doctor_id) then
update queue_summary
set num_of_patients = num_of_patients - 1
where date = date(old.actual_time) and doctor_id = old.doctor_id;
end if;
end $$
delimiter ;
存在检查完全是装饰性的,因为如果没有要删除的内容,删除不会抱怨。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.