Update table in a trigger with values from stored procedure - mysql

Question

I wanted to make a trigger which updates a table with the values of a procedure. I want the trigger to do something like this:
DELIMITER $$
CREATE TRIGGER onInsertVillage AFTER INSERT ON Village
FOR EACH ROW
BEGIN
UPDATE Village V SET V.xCoordinaat = x, V.yCoordinaat = y FROM getVrijePlaatsInMap();
END$$
DELIMITER ;
But this doesn't work.. The procedure returns an x and y value by the way. Is there a possible way to make the trigger do it's job?

Answer 1

I suppose that the trigger shall adapt xCoordinaat and yCoordinat for every new village inserted into table Village. If this is the case, I would use an BEFORE INSERT-trigger, which has access to the values of the respective village record to be inserted (before it is inserted). In absence of schema and stored procedure code of your example, I wrote a simplified program demonstrating this approach:
create table test (
a int,
b int,
c int
);
CREATE PROCEDURE simpleproc (IN a int, OUT b INT, OUT c int)
BEGIN
set b = a div 100;
set c = a % 100;
END;
CREATE TRIGGER test_before_insert
BEFORE INSERT
ON test FOR EACH ROW
BEGIN
call simpleproc (new.a,new.b,new.c);
END;
insert into test (a,b,c) values (120,0,0), (210,0,0), (303,0,0);
this yields:
a | b | c
----|---|---
120 | 1 | 20
210 | 2 | 10
303 | 3 | 3
Getting your approach working might be a little bit more tricky; In an AFTER INSERT-trigger, you have access to the .NEW-values, but you cannot modify them; Hence, you have to do an update on the table, but you somehow have to identify the village that has just been inserted.