I am trying to add a trigger to my SQL DB from phpMyAdmin.
When applying the trigger:
CREATE TRIGGER `download_url` AFTER INSERT ON
`tbl_files` FOR EACH ROW UPDATE tbl_files SET
download = CONCAT('http://website/', url)
WHERE 1
When trying to upload a file, I get no results; if I remove the trigger it functions properly. I need the download column to update with the prefix [http://website/] and value [url].
Thank you!!!
You can use a considerably simpler approach - instead of having an AFTER INSERT trigger, use a BEFORE INSERT trigger and manipulate the incoming row before writing it to the table. You can use the special variable NEW to reference this new row:
CREATE TRIGGER download_url
BEFORE INSERT ON tbl_files
FOR EACH ROW
SET NEW.download = CONCAT('http://website', NEW.url);
END;
Related
I need to write a SQL trigger whenever (engage_step_user_response) table (response_json)
column updated, I need to increase no of retakes by one in the retakes column. I have tried to write a SQL trigger referencing some details. But it doesn't succeed. can anyone please help regarding this?
CREATE TRIGGER increment_engage
ON engage_step_user_response
AFTER UPDATE
AS
IF UPDATE(response_json)
FOR EACH ROW
SET NEW.retakes = OLD.retakes + 1
I'm expecting whenever the response_json column is updated retakes must be increase by one.enter image description here
Try this :
You will need a BEFORE UPDATE trigger if you want to modify the data:
CREATE TRIGGER increment_engage BEFORE UPDATE ON engage_step_user_response
FOR EACH ROW
BEGIN
IF !(NEW.response_json <=> OLD.response_json) THEN
SET NEW.retakes = NEW.retakes+1;
END IF;
end;
demo here
CREATE TRIGGER increment_engage
BEFORE UPDATE ON engage_step_user_response
FOR EACH ROW
SET NEW.retakes = OLD.retakes + NOT (NEW.response_json <=> OLD.response_json);
the code is null-safe.
I'm using SQLite 3.37.2 through Python 3.10.5, and editing the database with DBeaver - maybe it's not always at its best when reporting database errors.
Anyway, I want to convert a text (JSON) in SQLite proper JSON format upon insertion, by calling its json() function.
I thought about adding a simple trigger to handle that, but I can't figure out what's wrong in my syntax:
CREATE TRIGGER t1_before_insert AFTER INSERT ON t1 FOR EACH ROW
BEGIN
SET NEW.json:=json(NEW.json);
END
;
This is the latest version I attempted, I always get an error like
SQL error or missing database (near "SET": syntax error)
I tried:
SET NEW.json:=json(NEW.json)
SET NEW.json=json(NEW.json)
SELECT NEW.json:=json(NEW.json)
using an AFTER INSERT trigger
but none worked.
You can't change the value of a column of the new row like that.
You must update the table in an AFTER INSERT trigger:
CREATE TRIGGER t1_after_insert AFTER INSERT ON t1 FOR EACH ROW
BEGIN
UPDATE t1
SET json = json(NEW.json)
WHERE t1.id = NEW.id;
END;
Change id to the table's primary key.
See the demo.
I've been trying to create a MySQL Trigger in order to set a random value to a column called confcode which is used for authentication purposes.
The issue is, the value never sets after I insert a new row and keeps being empty.
I use phpMyAdmin to create the trigger, and these are the defines:
Trigger name: confcode
Table: ebaysales
Time: BEFORE/AFTER (both don't work)
Event: INSERT
Definition: SET #confcode = FLOOR(RAND()*999999)+111111
The trigger itself gets inserted successfully, but doesn't seem to affect anything..
I guess you want:
SET NEW.confcode = FLOOR(RAND()*999999)+111111;
-- instead of
SET #confcode = FLOOR(RAND()*999999)+111111;
I'm trying to create a trigger that everytime that insert a new data in my table tb_produto_parent, I need to update the columm cod_prod add one more.
Follow the trigger :
DELIMITER $$
create trigger trgAdicionaUm after insert
on tb_produto_parent
for each row
BEGIN
select cod_prod from tb_produto_parent;
update
tb_produto_parent set cod_prod = cod_prod +1;
END;
When I try to execute the code, MySQL show me a error :
Error Code: 1415 Not allowed to return a result set from a trigger.
Thanks !
There are two major problems with your code
you can't use SELECT on it own in a trigger because a trigger doesn't return a resultset to the client
you can't use DML statements (UPDATE in your case) on the same table (tb_produto_parent) on which you have your trigger in MySQL. Therefore even if you fix the first problem you still won't be able to update any row in tb_produto_parent within the trigger.
The only thing you can do in MySQL trigger is to alter values of columns of a row being inserted by using a BEFORE event for a trigger.
A possible solution is to use a stored procedure instead.
Error Code: 1415 Not allowed to return a result set from a trigger.
Looking at your trigger:
BEGIN
select cod_prod from tb_produto_parent;
update
tb_produto_parent set cod_prod = cod_prod +1;
END;
It would seem the select statement is the cause of this error. Remove it.
I'm trying to calculate the percentage column in my table project after an update occurs on any of the following columns fund and goal.
This is the query I made up:
CREATE TRIGGER percentcalc AFTER UPDATE ON project
FOR EACH ROW
SET percent = ( fund / goal ) *100
but I seem to get an error:
#1193 - Unknown system variable 'percent'
delimiter //
CREATE TRIGGER percentcalc AFTER UPDATE ON project
FOR EACH ROW BEGIN
SET NEW.percent = ( NEW.fund / NEW.goal ) * 100;
END
//
delimiter ;
There are two major problems:
You have to use NEW keyword to access values of columns of a row that is being updated
You can't change values of NEW variables in an AFTER trigger. If you try to do so you'll get 'Updating of NEW row is not allowed in after trigger' error. Therefore you have to use only BEFORE event for your trigger
Trigger Syntax and Examples
...Within the trigger body, the OLD and NEW keywords enable you to
access columns in the rows affected by a trigger. (OLD and NEW are not
case sensitive.)...
...In a BEFORE trigger, you can also change its value
with SET NEW.col_name = value if you have the UPDATE privilege for it.
This means you can use a trigger to modify the values to be inserted
into a new row or used to update a row. (Such a SET statement has no
effect in an AFTER trigger because the row change will have already
occurred.)...
That being said your trigger should look like
CREATE TRIGGER percentcalc
BEFORE UPDATE ON project
FOR EACH ROW
SET NEW.percent = (NEW.fund / NEW.goal) * 100;
Here is SQLFiddle demo