MYSQL multiple event in a trigger

Question

How can I create a trigger for this two CHECK constraint

create table section ( course_id varchar(8), 
    sec_id varchar(8), 
    semester varchar(6) 
    check (semester in ('Fall', 'Winter', 'Spring', 'Summer')), 
    year numeric(4,0) 
    check (year > 1701 and year < 2100), 
    building varchar(15), 
    room_number varchar(7), 
    time_slot_id varchar(4), 
    primary key (course_id, sec_id, semester, year), 
    foreign key (course_id) references course on delete cascade, 
    foreign key (building, room_number) references classroom on delete set null);

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Except for a solution.

Answer 1

Uzzal,

As explained in the article, " Validating data using a TRIGGER ," you should use a BEFORE INSERT trigger to validate your data, like so:

-- validate semester
CREATE TRIGGER `semester_validate_semester_insert`
    BEFORE INSERT
    ON `section`
    FOR EACH ROW
    BEGIN
            IF NEW.`semester` NOT IN ('Fall', 'Winter', 'Spring', 'Summer') THEN
        SIGNAL SQLSTATE VALUE '45000'
            SET MESSAGE_TEXT = '[table:section] - `semester` column is not valid';
    END IF;
END;

and

-- validate year
CREATE TRIGGER `semester_validate_year_insert`
    BEFORE INSERT
    ON `section`
    FOR EACH ROW
    BEGIN
            IF NEW.`year` <= 1701 OR NEW.`year` >= 2100) THEN
        SIGNAL SQLSTATE VALUE '45000'
            SET MESSAGE_TEXT = '[table:section] - `YEAR` column is not valid';
    END IF;
END;

Please let me know if you have any questions!