I am new to this and cant seem to find a situation similar to mine and Im sure the answer is simple.
I have two columns, one is a predefined licenseplate ("licenseplate") and one that will be a user inputted licenseplate ("enterlicenseplate").
I made a third column which will be the sort of error check column and will have its values inputted by a trigger. Basically if the entered license plate is the same as the predefined licenseplate, set that third column to 0, if the entered license plate is null(not inputted anything yet( set that to 1, and if theres values in both and they dont match, set it 2. But i keep getting script errors. Not sure if its my syntax or im going about this all wrong.
I appreciate any help!
CREATE TRIGGER MatchPlateOnUPDATE
BEFORE UPDATE ON wp_wpdatable_3
FOR EACH ROW
BEGIN
IF (NEW.enterlicenseplate is NULL) THEN
UPDATE wp_wpdatatable_3
SET MatchingPlates = 0;
ELSEIF (NEW.enterlicensplate = New.licenseplate) THEN
UPDATE wp_Wpdatatable_3
SET MatchingPlates = 1;
ELSE UPDATE wp_Wpdatatable_3
SET MatchingPlates = 2;
END
Your problem with the if statement is that you are missing closing end if;.
But there is more: a trigger cannot action the table it was fired upon - and even if it could, then your query would basically update all rows in the table, since your updates have no where clause.
Here, you just need to modify the value of column matchingPlates in the record that is about to be inserted:
delimiter //
create trigger matchplateonupdate
before update on wp_wpdatable_3
for each row
begin
if new.enterlicenseplate is null then
set new.matchingplates = 0;
elseif new.enterlicensplate = new.licenseplate then
set new.matchingplates = 1;
else
set new.matchingplates = 2;
end if;
end;
//
delimiter ;
I tried to create below Trigger but I have an Error.
Can I Use Update or use 'case when' in trigger?
Please help me to fix my issue here.
Code Explanation:
I want to update my existing row after insert or update.
Do not change the 'FUSDate1' or 'FUSDate2' If I didn't add anything to the 'FUSDate1' or 'FUSDate2'
Update the FUSDate to the New One or Inserted one If I Updated or inserted data to FUSDate
Code:
delimiter //
create trigger SafetyCertificationTRG
after insert on SafetyCertification
for each row
begin
case when (FUSDate1='' or FUZDate1 is NULL) then (FUZDate1=OLD.FUSDate1) else (update SafetyCertification set FUZDate1=NEW.FUSDate1) end;
case when (FUSDate2='' or FUZDate2 is NULL) then (FUZDate2=NEW.FUSDate2) else (update SafetyCertification set FUZDate2=NEW.FUSDate2) end;
end //
delimiter ;
Edit: I am going to add some information here to make the question more clear.
I have one column as FUS that can be get these 3 values only:('FUS1', 'FUS2' and 'FUS3')
I have 3 other columns: FUSDate1, FUSDate2, FUSDate3.
I want to save the Current Date to The FUSDate1 Or FUSDate2 Or FUSDate3 based on the user User Selection of FUS. (They are in same Table)
I used the provided answer and change it to this but I cannot do the above.
Code: This code is just for FUS1 and FUSDate1
delimiter //
CREATE TRIGGER SafetyCertification_bu
BEFORE UPDATE ON SafetyCertification
FOR EACH ROW
BEGIN
-- detect a change made to a value in col
IF OLD.FUS <=> NEW.FUS THEN
-- value of col is not changed, so do nothing
DO 0;
ELSE
-- we detected a new value was assigned to col
IF OLD.FUS ='%FUS1%' THEN
-- we can override the new value, keep it the same
SET NEW.FUSDate1 = CURDATE();
END IF;
END IF;
END //
delimiter ;
Another code that I expected to do my work but still have problem, Does not update Like above Code:
delimiter //
CREATE TRIGGER SafetyCertification_bu
BEFORE INSERT ON SafetyCertification
FOR EACH ROW
BEGIN
IF NEW.FUS='%FUS1%' THEN
SET new.FUSDate1=MD5(CURDATE());
END IF;
END //
delimiter ;
Update 3:
The Third code that provided in answer does not add anything to the FUSdate1 and 2 and 3 when i update or insert any data.
Code
DELIMITER $$
CREATE TRIGGER SafetyCertification_bu
BEFORE UPDATE ON SafetyCertification
FOR EACH ROW
BEGIN
-- set one of the `fusdateN` columns to current date
-- which column to set depends on the value assigned to `fus`
IF NEW.fus = 'FUS1' THEN
SET NEW.fusdate1 = DATE(NOW());
ELSEIF NEW.fus = 'FUS2' THEN
SET NEW.fusdate2 = DATE(NOW());
ELSEIF NEW.fus = 'FUS3' THEN
SET NEW.fusdate3 = DATE(NOW());
END IF;
END$$
DELIMITER ;
A couple of notes:
A trigger cannot issue an UPDATE against the table that fired the trigger, this is prohibited.
The unqualified references (e.g. FUSDate1 and FUZDate1) are not valid. Those references don't resolve to anything.
The reference to OLD.FUSDate1 is invalid in the context of an AFTER INSERT trigger. In an UPDATE trigger, the OLD.col refers to the value of col before the update.
The expression (FUZDate1=OLD.FUSDate1) is not an assignment, it's a comparison that's going to return 0, 1 or NULL.
If we want to trigger on an UPDATE and an INSERT, that will require two separate triggers.
If we want to modify the contents of the current row, we can use BEFORE trigger instead of AFTER.
I want to update my existing row after insert or update.
It would be much easier to apply changes before the row is inserted or updated. We can assign a value to a column col by referencing NEW.col in an assignment in a BEFORE INSERT or BEFORE UPDATE trigger. For example:
SET NEW.col = expr;
Do not change the FUSDate1 or FUSDate2 If I didn't add anything to the FUSDate1 or FUSDate2
This seems pretty straightforward. Just don't make any assignments to NEW.FUSDate1 or NEW.FUSDate2.
Update the FUSDate to the New One or Inserted one If I Updated or inserted data to FUSDate
The example proposed trigger contains references to FUZDate1 or FUZDate2, but there's no mention of these columns in the specification. The specification is confusing.
An UPDATE statement will assign a value to a column, no need for a trigger to do that. An INSERT statement can assign a value to a column, again, no need for a trigger for that.
The specification is not clear. Providing example starting state (rows in the table), and example INSERT or UPDATE statements, and the desired state after the statement is executed would go a long ways towards clarifying the requirements.
A demonstration of a BEFORE UPDATE trigger that prevents a new value being assigned to a particular column:
DELIMITER $$
CREATE TRIGGER SafetyCertification_bu
BEFORE UPDATE ON SafetyCertification
FOR EACH ROW
BEGIN
-- detect a change made to a value in col
IF OLD.col <=> NEW.col THEN
-- value of col is not changed, so do nothing
DO 0;
ELSE
-- we detected a new value was assigned to col
IF OLD.col IS NOT NULL THEN
-- we can override the new value, keep it the same
SET NEW.col = OLD.col;
END IF;
END IF;
END$$
DELIMITER ;
For what this example trigger achieves, we don't necessarily need that many IF conditions; those are included as a demonstrate some of the checks we can perform, how we can make references to the existing value of col and the new value assigned to col.
FOLLOWUP
Based on the update information in the question, here's an example of a BEFORE UPDATE trigger that satisfies the specification.
This is for the UPDATE action. To get this same behavior with an INSERT statement, this trigger definition needs to be repeated, with BEFORE INSERT in place of BEFORE UPDATE.
(I would use the name _bu for the before update trigger, and _bi for before insert trigger.)
DELIMITER $$
CREATE TRIGGER SafetyCertification_bu
BEFORE UPDATE ON SafetyCertification
FOR EACH ROW
BEGIN
-- set one of the `fusdateN` columns to current date
-- which column to set depends on the value assigned to `fus`
IF NEW.fus = 'FUS1' THEN
SET NEW.fusdate1 = DATE(NOW());
ELSEIF NEW.fus = 'FUS2' THEN
SET NEW.fusdate2 = DATE(NOW());
ELSEIF NEW.fus = 'FUS3' THEN
SET NEW.fusdate3 = DATE(NOW());
END IF;
END$$
DELIMITER ;
second followup
To answer the question about using CASE WHEN statement in the context of a MySQL stored program...
We could implement the example trigger (directly above in this answer) replacing the IF-THEM with either of the two forms of the CASE statement.
either
CASE
WHEN NEW.fus = 'FUS1' THEN
SET NEW.fusdate1 = DATE(NOW());
WHEN NEW.fus = 'FUS2' THEN
SET NEW.fusdate2 = DATE(NOW());
WHEN NEW.fus = 'FUS3' THEN
SET NEW.fusdate3 = DATE(NOW());
END CASE;
-or-
CASE NEW.fus
WHEN 'FUS1' THEN
SET NEW.fusdate1 = DATE(NOW());
WHEN 'FUS2' THEN
SET NEW.fusdate2 = DATE(NOW());
WHEN 'FUS3' THEN
SET NEW.fusdate3 = DATE(NOW());
END CASE;
note
The CASE statement is available in MySQL stored programs; outside of a stored program, it is not a valid SQL statement.
Also, we should not confuse this CASE statement with the CASE expression. The CASE expression is valid in the context of a SQL statement, such as a SELECT or UPDATE statement.
DEMONSTRATION
"I examined the Trigger, But unfortunately does not save anything in fusDates."
#Christiano: here is a simple demonstration
create table
CREATE TABLE `safety_certification`
( id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY
, fus VARCHAR(5)
, fusdate1 DATE
, fusdate2 DATE
, fusdate3 DATE
) ENGINE=INNODB
;
populate table with demonstration rows
INSERT INTO `safety_certification` (id, fus, fusdate1, fusdate2, fusdate3) VALUES
( 1, '', NULL, NULL, NULL)
,( 2, '', NULL, NULL, NULL)
,( 3, '', NULL, NULL, NULL)
,( 4, '', NULL, NULL, NULL)
,( 5, '', NULL, NULL, NULL)
;
create trigger
DELIMITER $$
CREATE TRIGGER `safety_certification_bu`
BEFORE UPDATE ON `safety_certification`
FOR EACH ROW
BEGIN
-- set one of the `fusdateN` columns to current date
-- which column to set depends on the value assigned to `fus`
IF NEW.fus = 'FUS1' THEN
SET NEW.fusdate1 = DATE(NOW());
ELSEIF NEW.fus = 'FUS2' THEN
SET NEW.fusdate2 = DATE(NOW());
ELSEIF NEW.fus = 'FUS3' THEN
SET NEW.fusdate3 = DATE(NOW());
END IF;
END$$
DELIMITER ;
updates will exercise BEFORE UPDATE trigger we just defined
UPDATE `safety_certification` sc SET sc.fus = 'FUS1' WHERE sc.id = 1 ;
UPDATE `safety_certification` sc SET sc.fus = 'FUS2' WHERE sc.id = 2 ;
UPDATE `safety_certification` sc SET sc.fus = 'FUS3' WHERE sc.id = 3 ;
UPDATE `safety_certification` sc SET sc.fus = 'FUS4' WHERE sc.id = 4 ;
display contents of table
SELECT * FROM `safety_certification`;
returns:
id fus fusdate1 fusdate2 fusdate3
------ ------ ---------- ---------- ------------
1 FUS1 2018-05-04 (NULL) (NULL)
2 FUS2 (NULL) 2018-05-04 (NULL)
3 FUS3 (NULL) (NULL) 2018-05-04
4 FUS4 (NULL) (NULL) (NULL)
5 (NULL) (NULL) (NULL)
seems like the trigger is populating the columns fusdate1, fusdate2 and fusdate3 per the specification, when some particular values are assigned to fus
I had a same problem and I used two trigger,
First trigger send data to the other table, so now you can create another trigger to send this data to the first table. I think it is low performance but it is the only way that I reached to it. I hope others have another solution for u.
I want to add a trigger if name has update with "NEW_" string. Below is my current trigger but its working without checking the updated value contain "NEW_" . please advice
if user updates name from "Ann" to "NEW_Ann" trigger should work.
if user updates name from "Ann" to "Ann111" trigger shouldn't work
Code:
$this->execute("ALTER TABLE `users`
ADD COLUMN `date_` TIMESTAMP NULL DEFAULT NULL");
$this->execute("CREATE TRIGGER `update_user_deleted_date` BEFORE UPDATE ON `users` FOR EACH ROW BEGIN
IF (NEW.name!= OLD.name) THEN
SET NEW.date_deleted = NOW();
END IF;
END ;");
Use this:
CREATE TRIGGER update_user_deleted_date BEFORE UPDATE ON users
FOR EACH ROW BEGIN
IF (LOCATE('NEW_', NEW.name) != 0) THEN
SET NEW.date_deleted = NOW();
END IF;
END;
LOCATE('NEW_', NEW.name) != 0 means that the location of string "NEW_" is found
I want to do something like this:
DECLARE VAR_NAME INT DEFAULT 0;
IF NEW.field_name != NULL THEN
SET VAR_NAME := 8;
END IF;
IF NEW.field_name = NULL THEN
SET VAR_NAME := 1;
END IF;
UPDATE table_name SET column_name = column_name + VAR_NAME WHERE table_id = NEW.given_id;
I have a trigger for when inserting a new value:
I declare a variable, I change its value based on some conditions and then I update a table by adding this value to the current value of a specific column where the condition is met 'table_id = NEW.given_id'
Even I don't get errors the desired result is not happening.
Right, as the comments indicate, you can't check for NULL with normal equality operators. The way that I understand this is that nothing is equal to, less than, or greater than, etc, NULL, as NULL is literally 'no value'.
You must instead use IS NULL or IS NOT NULL to check for NULL.
This link goes into further detail:
http://dev.mysql.com/doc/refman/5.7/en/working-with-null.html
I have the following trigger
CREATE TRIGGER `qc_date_trigger` AFTER UPDATE ON `brand`
FOR EACH ROW BEGIN
IF NEW.brandQC = '1' THEN
SET #brandQCDate = CURDATE();
ELSE
SET #brandQCDate = NULL;
END IF;
END
For some reason it does not update my Date field into the current date when QC is = 1. I've checked the mysql doc and it should work. Any ideeas?
If your column is named brandQCDate, then remove the #. The # makes it a user defined variable, not the column. Also you want to make this a BEFORE UPDATE trigger.
CREATE TRIGGER `qc_date_trigger` BEFORE UPDATE ON `brand`
FOR EACH ROW BEGIN
IF NEW.brandQC = '1' THEN
SET NEW.brandQCDate = CURDATE();
ELSE
SET NEW.brandQCDate = NULL;
END IF;
END