DELIMETER $$
CREATE EVENT loan_balance ON SCHEDULE EVERY '1' MONTH AND '5' DAYS
DO BEGIN UPDATE users SET loan_balance = total_loans_collected -
total_loans_paid;
END$$
DELIMETER;
Hello! I want to update this table on the 5th of every month and not just monthly. The "AND '5' DAYS isn't making it work.
You need a slightly different ON SCHEDULE phrase.
AT '2018-04-01 03:01' + INTERVAL 5 DAY EVERY MONTH
fires your event at 03:01 local time on the fifth day of every month.
03:01 is a good time for a scheduled job because it doesn't get messed up by standard-time / daylight-time switchovers.
Instead of using a trigger to update the loan_balance column, you can turn it into a generated column.
ALTER TABLE users MODIFY COLUMN loan_balance INT GENERATED ALWAYS AS
(total_loans_collected - total_loans_paid) STORED;
Unless I'm missing something, I believe this is the most optimal approach, and it is certainly easier to maintain.
Related
I'm wondering if there is any way to schedule an update where I update a tables data on expiration of the old one.
E.g. John Smith has an active service at Company X, but wants to upgrade the service. However, due to restrictions to his current agreement the new service doesn't take effect until X days.
Is there any way to store the new data and update it at the end of a month in MySQL? If yes, would this require me to have another table with the new order data stored?
Often this requirement for changing things at future times is handled by placing start_date and end_date columns in your services table.
Then you can find presently active service rows with
SELECT user_id, whatever, whatelse
FROM services
WHERE (start_date IS NULL OR start_date <= NOW())
AND (end_date IS NULL OR end_date > NOW());
You can, if you wish, create a view called active_services automatically filtering the services table for currently active services.
CREATE VIEW active_services AS
SELECT *
FROM services
WHERE (start_date IS NULL OR start_date <= NOW())
AND (end_date IS NULL OR end_date > NOW());
Note -- in this design end_date contains not the last moment the service is active but the first moment it becomes inactive. If end_date is null the service continues to be active.
To change a service or user_id at the beginning of next month you do these two operations:
UPDATE service
SET end_date = LAST_DAY(NOW()) + INTERVAL 1 DAY
WHERE user_id = <<user id you wish to change >>
INSERT INTO service (start_date, user_id, whatever, whatelse)
VALUES (LAST_DAY(NOW()) + INTERVAL 1 DAY,
<<user id you wish to change >>,
<<whatever>>,
<<whatelse>>;
Then, when next month arrives the active_services view returns the new service. This is much more robust than relying on a precisely timed monthly job. If you do a monthly job, it can run anytime. It simply cleans up expired services.
You can use MySQL events to run particular jobs at appointed times. (But some shared MySQL systems don't let you use events.)
Interestingly mysql has event schedulers have a look at the documentation.
below is an example of a minimal CREATE EVENT statement:
CREATE EVENT myevent
ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
DO
UPDATE myschema.mytable SET mycol = mycol + 1;
The previous statement creates an event named myevent. This event executes once—one hour following its creation—by running an SQL statement that increments the value of the myschema.mytable table's mycol column by 1.
If yes, would this require me to have another table with the new order data stored
I am not sure if you need another table or so...it purely depends on how you want it to be one
I want to create table with name "dynamicdate" in which first column name is "datecolumn" which will contain 15 rows i.e. first row should represent today's date for example 08/08/2017 and following column shows subsequent date for example, 08/09/2017, 08/10/2017 till 15th row contains 08/23/2017.
Question 1: How do I fill 15 rows in a column with consecutive date simultaneously.
Now, for example date becomes 08/09/2017 (because august 8 is over) is the today'date and 08/24/2017 is date of 15th day.
Question 2: How do i update database everyday dynamically i.e. without querying database.
This you can do by creating a job. Every morning or night schedule this Job.
A job will execute this procedure "p_Update_dynamicdate".
create proc dbo.p_Update_dynamicdate
as
Begin
Declare #date as datetime, #count as int
set #date =getdate()
set #count =1
truncate table dynamicdate --Delete old data
while #count<=15
Begin
insert into dynamicdate(Ddate)
select Dateadd(d,#count,getdate())
set #count=#count+1
End
End
Solution to problem #1 :
Already solved on StackOverflow :
MySQL - How can I add consecutive dates to many existing records?
Solution to problem #2 :
Please look at Schedule and events on MySql documentation :
https://dev.mysql.com/doc/refman/5.7/en/event-scheduler.html
syntax: CREATE EVENT my_event
ON SCHEDULE
EVERY 1 DAY
STARTS '2014-04-30 00:20:00' ON COMPLETION PRESERVE ENABLE
DO
# Your Update query
Please refer to below links for similar problem solution :
https://dba.stackexchange.com/questions/64208/scheduling-an-event-every-day-at-a-given-time
How to schedule a MySQL query?
Lets say I have a Table tbl_Room with a column taken (boolean) and a Customer wants to rent this room for a short period.
Now, can I tell mysql to change the value of taken automatically depending on the timestamp, e. g. if the rent time/period is over, the value of taken should set automatically to false.
Or do I need to update my database with CRON or some other script that runs on the server periodically?
Please use mysql event to manage it.
CREATE EVENT [IF NOT EXIST] event_name
ON SCHEDULE schedule
DO
event_body
Reference
Under event_body you can write select statement to check period and then update table if period is over.
The best way to handle this sort of time-based request is counterintuitive.
Don't try to update the table at a specific time. Instead, include a timestamp column called something like lease_expires_at.
When you rent a room, update the row to set the value of lease_expires_at to the time at which the rental period expires. For example, if you rent a room for 30 minutes, starting now, do this.
UPDATE room
SET lease_expires_at = NOW() + INTERVAL 30 MINUTE
WHERE room_number = whatever
If you want to know whether a room is presently (NOW()) taken, do this:
SELECT room_number,
CASE WHEN lease_expires_at IS NULL THEN 0
WHEN lease_expires_at <= NOW() THEN 0
ELSE 1 END taken
FROM room
WHERE room = whatever
If you want to know whether a room will be available one hour from now (NOW() + INTERVAL 60 MINUTE), do this:
SELECT room_number,
CASE WHEN lease_expires_at IS NULL THEN 0
WHEN lease_expires_at <= NOW() + INTERVAL 60 MINUTE THEN 0
ELSE 1 END taken
FROM room
WHERE room = whatever
Then, once in a while, but not in any time-critical way, you can clean things up using a query like this
UPDATE room SET lease_expires = NULL WHERE lease_expires <= NOW()
You can use an event, or an overnight cronjob, or whatever you wish, to do this cleanup. The integrity of your application doesn't depend on exactly when this job runs.
The advantage of this should be clear: If you rely on some regularly running process to set an taken column value, and that process doesn't run or runs late, you get bad results. When you rely on the time, you get accurate results.
There's a small boundary-condition detail in this design. By using <= in my queries, I'm choosing to have the lease_expires_at timestamp represent the very first moment at which the room is available for another lease, not the last moment of the present lease. That's a handy choice, because if you put something like 2017-11-2017 11:00:00 into lease_expires_at, and somebody says "is the room available at 11:00?" you want to be able easily to say "yes." The guy who rented it at 10:30 gets it until the moment before 11:00.
you can use jquery time picker....after u can create a if loop in which JavaScript time function will check current time...to its original time...if condition is satisfied...we can change the mysql taken function
I have a MySQL database with one big table in it. After a while, it becomes too full and performance degrades. Every Sunday, I want to delete rows whose last update is older than a certain number of days ago.
How do I do that?
Make a Scheduled Event to run your query every night. Check out Event Scheduler as well.
CREATE EVENT `purge_table` ON SCHEDULE
EVERY 1 DAY
ON COMPLETION NOT PRESERVE
ENABLE
COMMENT ''
DO BEGIN
DELETE FROM my_table WHERE my_timestamp_field <= now() - INTERVAL 5 DAY
END
What is the table design? Do you have a column with a timestamp?
Assuming you do, you could use that timestamp value with a datediff(your_date,CURDATE()) in a delete command.
Delete from table where datediff(date_col, CURDATE ()) > your_num_days.
Self Answer
Make a web server that sends the following SQL to the database every weekend:
DELETE FROM table WHERE timestamp < DATE_SUB(NOW(), INTERVAL 7 DAY);
or
DELETE FROM table
WHERE timestamp < UNIX_TIMESTAMP(DATE_SUB(NOW(), INTERVAL 7 DAY))
I might need locking to prevent accumulation of jobs, like so:
DELIMITER //
CREATE EVENT testlock_event ON SCHEDULE EVERY 2 SECOND DO
BEGIN
DECLARE CONTINUE HANDLER FOR SQLEXCEPTION
BEGIN
DO RELEASE_LOCK('testlock_event');
END;
IF GET_LOCK('testlock_event', 0) THEN
-- add some business logic here, for example:
-- insert into test.testlock_event values(NULL, NOW());
END IF;
DO RELEASE_LOCK('testlock_event');
END;
//
DELIMITER ;
Final answer:
CREATE EVENT `purge_table` ON SCHEDULE
EVERY 1 DAY
ON COMPLETION NOT PRESERVE
ENABLE
COMMENT ''
DO BEGIN
IF GET_LOCK('purge_table', 0) THEN
DELETE FROM table WHERE timestamp < UNIX_TIMESTAMP(DATE_SUB(NOW(), INTERVAL 7 DAY));
END;
Maybe you can provide more information on how you are pushing the data to the DB and how you are working on the DB in general? Therefore we can help you and don't have to struggle with the dark...
I'll provide an easy solution: It's kind of workaround, but works:
Everytime you touch the data you update a time stamp in the updated rows.
Therefore you could easily filter them out every sunday.
UPDATE
The answer, the author provided by himself, was discussed at Stackoverflow and seems not to work in exactly that way, compare the discussion.
I have a table lets say:
tblHotel
id
start_date
end_date
rate
Now I want to write procedure for update records for date range, say for example I have data:
id start_date end_date rate
1 2016/01/01 2016/01/10 10
2 2016/01/11 2016/01/20 50
Now if a new date range and rate comes from supplier I want to update tables record like new range is.
start_date end_date rate
2016/01/05 2016/01/12 100
Now updated records should be like this:
id start_date end_date rate
1 2016/01/01 2016/01/04 10
2 2016/01/05 2016/01/12 100
3 2016/01/13 2016/01/20 50
I'm not going to write the code for you, but handling overlapping time frame is tricky. You need to handle this as different cases:
If nothing overlaps, then this is simple:
insert into tbl_Hotel(start_date, end_date, rate)
select $start_date, $end_date, $rate
from dual
where not exists (select 1
from tbl_Hotel h
where h.start_date <= $end_date and h.end_date >= $start_date
);
Easy . . . And in the stored procedure the where can be handled using if logic.
Then the hard part. There are four types of overlaps:
-------hhhhhhhhhhh--------
a) ---------xxxxx------------
b) -----xxxxxx---------------
c) ----------xxxxxx----------
d) --xxxxxxxxxxxxxxxxxxxxxx--
And, then it gets a bit more complicated because a new rate period could overlap with more than one existing period.
Arrrg! How do you approach this? Carefully and with test cases. You might even want to use a cursor (although there are non-cursor-based methods as well).
The idea is to pull out one overlapping existing period. Then, for that period handle the logic:
a) The existing period needs to be split into two parts (with appropriate end dates. Then the new reservation can just be added.
b) The start date of the existing period has to change to one more than the end date of the new one. Then the new one inserted.
c) The end date of the existing period has to change to one less than the start date of the new one. Then the new one inserted.
d) The old record is removed and the new one inserted.
As I say, good tests for your stored procedure are important, so you can actually check that it works.