I've got a table that I'm trying to set up for auto-processing updates to a linking table.
When a row is added to the auto-processing table (and there's logic in place for when that happens or doesn't happen), it adds a row that table and then a MySQL Trigger takes over.
The trigger is:
delimiter //
create trigger trg_auto_processing after insert on link_auto_processing
for each row
BEGIN
-- pause
do sleep(2);
-- update link_table
insert ignore into link_table (col_1, col_2) VALUES (NEW.col_1, NEW.col_2);
delete from link_table where col_1 = NEW.col_1 and col_2 != NEW.col_2;
END
//
DELIMITER ;
When testing this, the row is added to link_auto_processing table just fine, the trigger activates and it does the insert into link_table, but it doesn't do the delete.
To my understanding, it can't be a table-lock because it did the insert, So what am I missing here? I've tried putting the delete in a "before insert" trigger on the link_auto_processing table, but that doesn't work either.
I've even tried just updating the link_table with the trigger but that also doesn't work.
Insert works.
Delete doesn't work.
Update doesn't work.
Can't figure out why. Any thoughts?
Related
I'm having a little issue with a trigger in a MySQL database. I have a DB with two tables: "tasks" and "files". The "tasks" table have a field which is a foreign key of the primary key from the "files" table. It also sometimes may be null.
What I'm trying to acomplish is to delete in the first place a row in the "tasks" table, and after that delete the corresponding row in the "files" table using a trigger.
This is the trigger I'm using right now:
DELIMITER //
CREATE TRIGGER after_delete_file AFTER DELETE ON tasks
FOR EACH ROW
BEGIN
DECLARE fileId int;
SELECT file INTO fileId FROM tasks WHERE id=old.id;
DELETE FROM files WHERE id=fileId;
END;//
DELIMITER ;
The field "file" in the "tasks" table is the one containing the foreign key. In the examples I've been running, that field has never been null.
The problem is that the select statement always returns null. The delete statement that triggers this trigger goes fine, but the row in the "files" table is never deleted. I've tried to insert the "fieldId" variable on a testing table, and it's always saving a null value.
Is there any problem on that trigger? Maybe I'm trying to do something merely impossible?
All the help is much appreciated :)
Since it should be looping over each deleted row, why would this not work?
DELIMITER //
CREATE TRIGGER after_delete_file AFTER DELETE ON tasks
FOR EACH ROW
BEGIN
DELETE FROM files WHERE id=old.file;
END;//
DELIMITER ;
If that doesn't work, could try this:
DELIMITER //
CREATE TRIGGER after_delete_file AFTER DELETE ON tasks
FOR EACH ROW
BEGIN
DELETE FROM files INNER JOIN tasks ON files.id=tasks.file WHERE tasks.id=old.id;
END;//
DELIMITER ;
but I don't think that should be necessary.
AFTER delete means that the data is deleted, of course you can't find it. Try creating the trigger for BEFORE delete.
You could also more carefully use all of the old values rather than selecting from the table that was deleted from.
I have several tables in the database: Users, Profiles, Articles
I also have one table called Changes, which is used for administrative purposes. This table consists of id, table_name, and date_created.
What I need to do is whenever something is added, deleted or updated in a regular table (Users, Profiles, Articles), create a new row in the Changes with the name of the updated table and the current timestamps.
I've been browsing for a while and tried many different methods, but nothing really worked. I know the solution should be very simple, may be someone can help me. Thank you for your time.
So in this case you need 9 trigger 3 for each of the regular table after insert, after update, after delete
Here is for one table you can write for the others
When you insert on Users
delimiter //
create trigger log_user_insert after insert on Users
for each row
begin
insert into Changes (table_name,date_created) values ('Users',now());
end; //
delimiter ;
When update happens on Users
delimiter //
create trigger log_user_update after update on Users
for each row
begin
insert into Changes (table_name,date_created) values ('Users',now());
end; //
delimiter ;
When delete happens on Users
delimiter //
create trigger log_user_update after delete on Users
for each row
begin
insert into Changes (table_name,date_created) values ('Users',now());
end; //
delimiter ;
I would suggest to add a column called action in the table Changes and to insert each action name as well i.e. insert,update and delete.
You need to create an update, insert and delete trigger on each of the data tables:
CREATE TRIGGER upd_changes_users BEFORE UPDATE ON Users
FOR EACH ROW
BEGIN
INSERT INTO changes (table_name, date_created) VALUES ('users', NOW());
END;
This code assumes, that the id column in changes is auto_generated. You might also want to consider including a type column in the changes table (to differentiate between insert, update and delete).
MySql trigger is very interesting, but very tricky.
I have some problem, I want to run a trigger once after insert on .
I want to run my trigger once after rows inserted, is there anything like for each table``???
how to make this trigger run only once, but not for each row created.
CREATE
DEFINER=`root`#`localhost`
TRIGGER `mydb`.`leave_taken_trigger`
AFTER INSERT ON `mydb`.`leave`
FOR EACH ROW
BEGIN
set #lt:= (SELECT count(*) FROM `leave` where (staff_leave_application_staff_id_staff = new.staff_leave_application_staff_id_staff and leave_type_id_leave_type = new.leave_type_id_leave_type) and active = 1 );
INSERT INTO `leave_taken`(leave_type_id_leave_type, staff_id_staff, taken_days, updated)
VALUES (new.leave_type_id_leave_type, new.staff_leave_application_staff_id_staff, IFNULL(#lt,0), CURDATE())
ON DUPLICATE KEY UPDATE taken_days=IFNULL(#lt,0), updated = CURDATE();
END$$
I think you can't achieve your requirement with trigger.
Your trigger will run in every row created.
I suggest you to using stored procedure from your code after the INSERT has successfully completed.
I'm trying to create a trigger that will allow only one record in a database, so it would delete any previous records.
But currently, it doesn't allow me to insert anything it, because it's instantly deleted.
DELIMITER $$
CREATE TRIGGER test_insert
BEFORE INSERT ON test
FOR EACH ROW BEGIN
DELETE FROM test WHERE id = NEW.id - 1;
END$$
How would I delete a previously (or all previous) inserted record?
"But currently, it doesn't allow me to insert anything it, because it's instantly deleted."
Acutally, when you do an INSERT, the execution of your trigger should be throwing exception:
Error Code: 1442
Can't update table 'test' in stored function/trigger because it is
already used by statement which invoked this stored function/trigger.
(Unless something is radically different in a newer version of MySQL.)
The operation you want to perform (i.e. deleting rows from the same table you are inserting into) cannot be done in a MySQL trigger.
You could use a combination of a UNIQUE KEY and a BEFORE INSERT trigger to prevent more than one row from being inserted. The BEFORE INSERT trigger could set the value of the column that has a unique
key on it to be a static value, then the INSERT statement would throw a duplicate key ("Duplicate entry") exception.
Then, you could use an INSERT ... ON DUPLICATE KEY UPDATE ... statement to update the values of columns other than the unique id, e.g.
CREATE TRIGGER `test_insert` BEFORE INSERT ON test
FOR EACH ROW BEGIN
SET NEW.id := 1;
END
ALTER TABLE test ADD UNIQUE KEY (id);
INSERT INTO test (somecol) VALUES ('someval')
ON DUPLICATE KEY UPDATE somecol = VALUES(somecol) ;
To do that you first need to find some value at which you want to delete all and insert for. This way you don't need a trigger, you simply delete all previous cases and then add a new row. Unless for some reason unexplained from your code you would need a trigger a simple solution in your loop could work Like:
$query = mysql_query("DELETE FROM test WHERE id = NEW.id -1");
$new_id = $new.id -1;
$query2 = mysql_query("INSERT INTO test VALUES('$new_id','$var1','$var2'));
I have the following trigger:
CREATE TRIGGER sum
AFTER INSERT
ON news
FOR EACH ROW
UPDATE news SET NEW.sum = (NEW.int_views + NEW.ext_views)/NEW.pageviews
It sums the int_views and ext_views column of a table and divides them by the total pageviews.
Whenever I try to add a new row to news, I get the following error:
ERROR 1442 (HY000) at line 3: Can't update table 'news' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.
The trigger seems pretty simple to me. Is there a reason why the trigger fails to run?
The symptom is, that you are running an UPDATE (for all rows) inside a INSERT trigger - both modify the table, which is not allowed.
That said, if I guess the intention of your trigger correctly, you do not want to update all rows, but only the newly inserted row. You can achieve that easily with
CREATE TRIGGER sum
BEFORE INSERT
ON news
FOR EACH ROW
SET NEW.sum = (NEW.int_views + NEW.ext_views)/NEW.pageviews
Mind that this is a BEFORE INSERT trigger, as you want to change the row before it is written to the table.
If you try to update/insert on the same table that cause trigger to fire do not use the common sql command like
-> UPDATE TABLE_NAME SET COLUMN_NAME = VALUE WHERE CONDITION_LIST;
-> INSERT INTO TABLE_NAME VALUES("VALUE1","VALUE2");
This will not work. Only use set to assign the value of the column you update.
Example:
CREATE TRIGGER trigger_name BEFORE/AFTER INSERT/UPDATE ON table_name
FOR EACH ROW
SET NEW.COLUMN_NAME = "VALUE";
I was in a similar condition where I had to run two triggers:
UPDATE 3 fields on INSERTing a new ROW
UPDATE 3 fields on UPDATEing a ROW
After lot of efforts, I was finally able to write the TRIGGER in following way:
FOR updating values on INSERT
CREATE TRIGGER `INSERT_DISCOUNT_SERVICES` BEFORE INSERT ON `services`
FOR EACH ROW SET
NEW.discount_5_rate = (NEW.ndis_rate*0.05),
NEW.discount_10_rate=(NEW.ndis_rate*0.10),
NEW.discount_15_rate=(NEW.ndis_rate*0.15)
Similarly
FOR updating values on UPDATE
CREATE TRIGGER `UPDATE_DISCOUNTS_SERVICES` BEFORE UPDATE ON `services`
FOR EACH ROW SET
NEW.discount_5_rate = (NEW.ndis_rate*0.05),
NEW.discount_10_rate=(NEW.ndis_rate*0.10),
NEW.discount_15_rate=(NEW.ndis_rate*0.15)