I am trying to figure out a conditional trigger for an update to a MySQL table.
The issue is that the update trigger fires off even when the data being entered is the same as the data that was already there. So if I have a column with a row:value set up like this plus_votes:2 if I update with UPDATE votes SET plus_votes = 2; even though nothing has really changed the UPDATE trigger still gets fired off. So to prevent all of this I want to add a conditional clause to my trigger like this
BEGIN
IF NEW.vote_value <> OLD.vote_value THEN
UPDATE my_other_table
SET plus_votes =
CASE NEW.vote_value WHEN '1'
THEN plus_votes + 1
ELSE plus_votes
END,
minus_votes =
CASE NEW.vote_value WHEN '1'
THEN minus_votes
ELSE minus_votes +1
END
WHERE my_other_table.id=NEW.votes_join_id;
END
END
the second half of the issue is that I have CASE condition inside the IF statement.
Can someone help on this issiu and show how to do nested conditionals inside a TRIGGER?
much appreciated
although the syntax you have posted is completely wrong, I have figured out what you want try this ( not tested )
DROP TRIGGER IF EXISTS upd_vote;
DELIMITER $$
CREATE TRIGGER upd_vote AFTER UPDATE ON `my_other_table`
FOR EACH ROW BEGIN
IF NEW.vote_value <> OLD.vote_value THEN
SET
NEW.plus_votes = IF(NEW.vote_value=1,OLD.plus_votes+1,OLD.plus_votes),
NEW.minus_votes = IF(NEW.vote_value=1,OLD.minus_votes,OLD.minus_votes +1 )
END IF;
END$$
DELIMITER ;
Related
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 am trying to use an attribute from a 2nd table in the trigger of the 1st. To do this I am trying to load that value into a variable and then use it as a comparison.
However whenever I try and test the process the comparison answers false.
DELIMITER $$
create trigger evolve_persona before update on phantom_thieves
for each row begin
set #t := (select tier from persona where pname = old.persona);
if((new.persona != old.persona) and (select cast(#t as unsigned) = '1')) then
set
new.st = old.st+10, new.ma = old.ma+10, new.en= old.en+10, new.ag= old.ag+10,
new.lu= old.lu+20;
end if;
end$$
DELIMITER ;
I can see nothing wrong with your trigger but, this is somewhat more complicated as be written in a comment.
Make please following
SET #t = -1;
SELECT #t; -- returns -1
update phantom_thieves SET .....
SELECT #t; -should display at sometime 1
This seems to be the only problem that tier don't has the response 1 and with above, you can see what you get.
I can't find the correct syntax for the trigger I tried to code.
I want to update a timestamp every time there is an update on the table but only for specific rows. I want to update the "UPDATE_TIME" only for the last "N_TACHE"
I can't find how to use SET with a where clause.
CREATE TRIGGER "time_on_update"
BEFORE UPDATE ON "SAVE_UPDATE"
FOR EACH ROW
BEGIN
IF
(NEW.DATE_DE_RDV <> OLD.DATE_DE_RDV)
OR
(NEW.ADRESSE <> OLD.ADRESSE)
OR
(NEW.CODE_POSTAL <> OLD.CODE_POSTAL)
OR
(NEW.VILLE <> OLD.VILLE)
THEN
SET (NEW.UPDATE_TIME = current_timestamp WHERE N_TACHE= (SELECT MAX(N_TACHE));
END IF;
If you have any suggestion I take it.
Thanks in advance
EDIT :
This one is working but it update all the rows and I just want to update "update_time" for the last value of "N_TACHE" when "RDV","ADRESSE","CODE_POSTAL" or "VILLE" is updated
DELIMITER $$
CREATE TRIGGER `time_on_update`
BEFORE UPDATE ON `SAVE_UPDATE`
FOR EACH ROW
BEGIN
IF
(SELECT MAX(N_TACHE)
FROM SAVE_UPDATE
WHERE
((NEW.DATE_DE_RDV <> OLD.DATE_DE_RDV)
OR
(NEW.ADRESSE <> OLD.ADRESSE)
OR
(NEW.CODE_POSTAL <> OLD.CODE_POSTAL)
OR
(NEW.VILLE <> OLD.VILLE)))
THEN
SET NEW.UPDATE_TIME = current_timestamp;
END IF;
END
$$
DELIMITER ;
How do I update 2 tables in single UPDATE SET, under some condition ?
If the condition is not met, I'd only update one table..
I'd like to do something like this:
UPDATE tab1, tab2 SET
tab1.value2=7,
CASE tab1.value1 IS NOT NULL
WHEN true
THEN tab2.value1 = tab1.value1
END
WHERE tab1.id=1 AND tab2.id = tab1.tab2_fk_id
MySQL workbench complains: Syntax Error: Unexpected CASE_SYM
I think I should do this with a TRIGGER - function
Here how you can do it,
update tab1 ,tab2
join tab2 on tab2.id = tab1.tab2_fk_id
set
tab1.value2=7,
tab2.value1 = case when tab1.value1 IS NOT NULL then tab1.value1 else tab2.value1 end
where tab1.id=1
Many thanx to Abhik Chakraborty for a brillant solution. It will be surely useful in other context. I have though decided to create a trigger in static_conveyor (~ tab1 in the above example) to achieve equal behavior. I use real tables and column names here instead of generic.. :
USE `tca`;
DELIMITER $$
CREATE DEFINER=`root`#`localhost` TRIGGER `static_conveyor_AUPD` AFTER UPDATE ON `static_conveyor` FOR EACH ROW
BEGIN
IF (OLD.signal != NEW.signal)
THEN
IF ((NEW.pallet_id IS NOT NULL) AND (NEW.default_empty IS NOT NULL))
THEN
UPDATE pallet SET empty = NEW.default_empty WHERE pallet.id = NEW.pallet_id;
END IF;
END IF;
END
Works nice ..
Looking for assistance crafting a mysql trigger. My current code does not work as intended. What I would like to do is if field A in table A is modified, copy field A to field B in table A.
Current code looks like this:
BEGIN
IF new.set_id=301 THEN
UPDATE lighting_io_settings SET slider1_val=new.val WHERE set_id=402;
END IF;
END
Obviously it fails because an update is calling an update.
On before update you can check the old tuple value on variable "OLD" and check the new tuple values on "NEW" variable.
BEGIN
IF NEW.columnA != OLD.columnA THEN
//do whatever you want here like
NEW.columnB = NEW.columnA;
//can call update again, just don't change the columnA
update tableA set columnB = NEW.columnA where id = 402;
END IF;
END