Question

I have seen MySQL triggers mentioned and I am curious whether they could be used for my scenario. That being:

lets say i have a table results_tb. Currently there is a field score and a field grade . So can I use triggers to update grade on the event of score changing?

so for example, lets say score stored was 40, the grade is updated to C, then again if the score is updated to 70, the grade is updated to A.

is this possible with triggers?

Answer 1

You can use a trigger if you want, however, I agree with Nanne in terms of what appears to be better approach in the situation described.

DELIMITER |

DROP TRIGGER /*!50032 IF EXISTS */ `trigger_update_results_tb`|

CREATE TRIGGER `trigger_update_results_tb` BEFORE UPDATE ON `results_tb` 
    FOR EACH ROW BEGIN
       CASE FLOOR(NEW.score / 10)
        WHEN 0 THEN SET NEW.grade = 'F';
        WHEN 1 THEN SET NEW.grade = 'F';
        WHEN 2 THEN SET NEW.grade = 'F';
        WHEN 3 THEN SET NEW.grade = 'F';
        WHEN 4 THEN SET NEW.grade = 'D';
        WHEN 5 THEN SET NEW.grade = 'C';
        WHEN 6 THEN SET NEW.grade = 'B';
        ELSE SET NEW.grade = 'A';
       END CASE;
    END;
|

DELIMITER ;