How to SELECT multiple values in MYSQL trigger? - mysql

Question

how can I SELECT multiple values INTO variables in MYSQL trigger?
I have tried SELECT values into variables in this way but it didn't work. I was inspired by this thread how to use trigger to set value based on query result.
When I examined value in variables, it is NULL. When I put this SELECT into mysql workbench it will select right values. I check column types and they are same type as variables in trigger.
With debug I discovered that there is problem with SELECTing values.
Thank you in advance.
Here is my trigger:
CREATE TRIGGER fin_den_zam_insert
AFTER INSERT
ON table1 FOR EACH ROW
BEGIN
DECLARE koef1 DECIMAL(6,3);
DECLARE koef2 DECIMAL(6,3);
DECLARE koef3 DECIMAL(6,3);
DECLARE sum DECIMAL(6,3);
SELECT DISTINCT
koef_salary, koef_sunday, koef_holiday
INTO
koef1 , koef2, koef3
FROM
employee E
WHERE
E.personal_number = NEW.personal_number_id;
SET sum := NEW.salary * (koef1 + koef2 + koef3);
INSERT INTO export_table
(
id_export,
personal_number,
final_sum
)
VALUES
(
NULL,
NEW.personal_number_id,
sum
);
END;
//
DELIMITER ;

Answer 1

You must be careful with reserved words like sum, that can cause very much trouble-
most people write before every own variable _ like _sum, so that also a stranger can identofy such variables.
That is as you can see not absoltely necessary, but helps also when you tale a look in 5 years
create table employee
(personal_number int,koef_salary DECIMAL(6,3), koef_sunday DECIMAL(6,3), koef_holiday DECIMAL(6,3));
create table export_table(
id_export int auto_increment primary key,
personal_number int,
final_sum DECIMAL(6,3)
);
CREATE table table1
(id_export int auto_increment primary key
, personal_number_id int
, salary DECIMAL(6,3));
insert into employee values(1,1.1,1.3,1.4);
CREATE TRIGGER fin_den_zam_insert
AFTER INSERT
ON table1 FOR EACH ROW
BEGIN
DECLARE koef1 DECIMAL(6,3);
DECLARE koef2 DECIMAL(6,3);
DECLARE koef3 DECIMAL(6,3);
DECLARE final_sum DECIMAL(6,3);
SELECT DISTINCT
koef_salary, koef_sunday, koef_holiday
INTO
koef1 , koef2, koef3
FROM
employee E
WHERE
E.personal_number = NEW.personal_number_id;
SET final_sum := NEW.salary * (koef1 + koef2 + koef3);
INSERT INTO export_table
(
id_export,
personal_number,
final_sum
)
VALUES
(
NULL,
NEW.personal_number_id,
final_sum
);
END
INSERT INTO table1 VALUES (NULL,1,100)
SELECT * FROM export_table
id_export | personal_number | final_sum
--------: | --------------: | --------:
1 | 1 | 380.000
db<>fiddle here