I have to limit table record to 25. after I just delete everything (in the future will modify it to delete just oldest rows)
DELIMITER //
CREATE PROCEDURE p1 () delete FROM tests;//
CREATE TRIGGER trigger1
BEFORE INSERT
ON tests
FOR EACH ROW
BEGIN
SELECT COUNT(*) INTO #cnt FROM tests;
IF #cnt >= 25 THEN
CALL p1();
END IF;
END
//
DELIMITER ;
, but I am getting error:
Can't update table 'tests' in stored function/trigger because it is already used by statement which invoked this stored function/trigger
So I can not add any more fields.
The MySQL trigger FAQ sais that you cannot modify the table that calls the trigger.
But you can set up a cron job, or CREATE EVENT in MySQL that cleans the table at regular intervals. (CREATE EVENT needs the PROCESS privilege, and a running event_scheduler. The event_scheduler is turned off by default: it can be turned on from SQL console, but the MySQL config must be modified to ensure that it starts when MySQL restarts.)
It seems that you can't update or delete from the same table which invoked the trigger.
But you can work around this by creating another table, for example tests2 and instead of inserting into tests just insert into tests2, and have the trigger insert the NEW. values into tests, then you can count from tests and delete from tests like how you want it.
see this sqlFiddle
The problem with this is then tests2 gets filled up with Inserted data So you might have to manually delete from tests2.
Related
I'm writing a query that creates a trigger to soft delete a row in the table customer using the a flag called "IsDelete" when the flag is '0' it is not deleted and when the flag becomes 1 the row has been marked as deleted.
When the query is run the error code 1442c is generated. can anyone explain why??
DELIMITER $$
CREATE TRIGGER SOFT_DELETE_TRIGGER
BEFORE DELETE ON customer
FOR EACH ROW
BEGIN
IF OLD.IsDelete = 0 THEN
CALL cannot_delete_error;
UPDATE customer
SET IsDelete = 1;
END IF;
END
$$
Deleting a row in the table to test the trigger.
DELETE FROM customer
WHERE C_username = 'testuser'
Yes, triggers don't allow you to INSERT/UPDATE/DELETE against the same table that spawned the trigger, because that could run invoke the trigger again, and then that trigger might do another INSERT/UPDATE/DELETE, and so on. You have too high a chance of causing an infinite loop.
I'm afraid MySQL doesn't support an "instead of" trigger like some other brands of SQL database do. You can't make a trigger on DELETE that does an update instead.
You can use SIGNAL to make it throw an error, and that blocks the DELETE, but it doesn't do an UPDATE instead.
To implement soft deletes as you are doing, you'll just have to make the client use UPDATE instead of DELETE.
Is there any way to delete a row inside trigger (on the table which fired the trigger) in MariaDB/MySQL?
I know it's possible to do so in postgres.
Here is the SQL I've tried.
TRIGGER trigger AFTER INSERT ON table FOR EACH ROW BEGIN
DELETE FROM table
WHERE expire_at <= CURRENT_TIMESTAMP;
END
I'm getting this error message:
Code: 1442. Can't update table 'cluster_events' in stored
function/trigger because it is already used by statement which invoked
this stored function/trigger.
Is it possible to solve this some other way?
If you want to periodically purge 'old' data, use an EVENT.
Be sure to turn on the Event Scheduler.
Problem is that, I want a trigger that deletes old rows in the same table that the new rows are being inserted into.
MsSQL and oracle can do this,
but looks like mySQL can't,
It allows the trigger to be created, but when it runs it gives the error
"can't update table "tbl" in stored procedure or function/trigger
because it is already used by statemtent whicgh invoked this stored
procedure or function/trigger"
Any work around for this?
Is it planned in future releases?
I have in my database all tables with filed name GHOST, so when GHOST is TRUE this row is like DELETED. So if You want change row after insert maybe use like this:
CREATE TRIGGER my_trigg
BEFORE INSERT ON table
FOR EACH ROW
BEGIN
SET NEW.ghost = TRUE;
END
$$
DELIMITER ;
After creating either of the triggers below I get the error (detailed after the code) when I try to do an update. No matter which way I go I seem to be unable to update the table. Do I have to create a new table and put one column in that for updating or is there a way around this? This page says: "Within a stored function or trigger, it is not permitted to modify a table that is already being used (for reading or writing) by the statement that invoked the function or trigger." But then what's the point of the NEW and OLD keywords? Am I just using them incorrectly?
table: gallery
columns: weight, modifier, rating
trigger: updateRating
CREATE TRIGGER updateRating
BEFORE UPDATE ON gallery
FOR EACH ROW
UPDATE gallery SET rating= sum(NEW.weight * NEW.modifier)
or
CREATE TRIGGER updateRating
AFTER UPDATE ON gallery
FOR EACH ROW
UPDATE gallery SET rating= sum(weight * modifier)
SQL query: Edit
UPDATE `acs`.`gallery` SET `weight` = '6' WHERE `gallery`.`id` =1 LIMIT 1
MySQL said: Documentation
#1442 - Can't update table 'gallery' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.
Right, error means that you cannot modify gallery table because the trigger was defined with this table. There is one possible way to update the value, it is a BEFORE UPDATE trigger, here it is an example -
CREATE TRIGGER updateRating
BEFORE UPDATE
ON gallery
FOR EACH ROW
BEGIN
SET NEW.rating= NEW.weight * NEW.modifier; -- You may update a NEW value.
END
At the end, let me ask a question. Why are you going to use a trigger to modify the rating? I want to say that you can calculate rating on the fly, in SELECT statement.
I am trying to create a MySQL Trigger to disable someone's account if they have logged in to the site 3 times. I have tried to create this trigger using the following code, but it is not setting is_active to 0 no matter what times_logged_in is. Any help would be appreciated.
CREATE TRIGGER updateTrigger AFTER UPDATE ON users
FOR EACH ROW
BEGIN
UPDATE users SET is_active=0 WHERE NEW.is_code=1
AND NEW.times_logged_in>=3
AND NEW.user_id=user_id;
END;
You've hit a limitation of MySQL. Your table users invokes the trigger (AFTER UPDATE ON users), therefore the triggered code cannot modify it. See the MySQL-Manual:
Within a stored function or trigger,
it is not permitted to modify a table
that is already being used (for
reading or writing) by the statement
that invoked the function or trigger.
I'm not sure where user_id comes from in your trigger, looks like an extraneous check, try this:
CREATE TRIGGER updateTrigger AFTER UPDATE ON users
FOR EACH ROW
BEGIN
UPDATE users SET is_active=0 WHERE NEW.is_code=1
AND NEW.times_logged_in>=3
END;
Also, be sure that is_code = 1 is actually matching on the users you're updating, if it's not, it won't update any rows.
I would use a BEFORE UPDATE trigger instead:
CREATE TRIGGER updateTrigger BEFORE UPDATE ON users
FOR EACH ROW
BEGIN
IF NEW.is_code=1 AND NEW.times_logged_in>=3 THEN
SET NEW.is_active=0;
END IF;
END;