-- https://www.youtube.com/watch?v=HXV3zeQKqGY&t=10461s
-- The end has ER diagrams and converting one to a schema.
-- On ER diagrams: https://www.mikedane.com/databases/sql/er-diagrams-intro/

-- This is too big to turn into a gquiz2 question, but it's interesting.  Note that this must be done in something
-- that can change the SQL delimiter, like the command line.
DELIMITER $$
CREATE
    TRIGGER my_trigger BEFORE INSERT
    ON employee
    FOR EACH ROW BEGIN
        INSERT INTO trigger_test VALUES('added new employee');
    END$$
DELIMITER ;


-- Insert the new records' first names into trigger_test:
DELIMITER $$
CREATE
    TRIGGER my_trigger BEFORE INSERT
    ON employee
    FOR EACH ROW BEGIN
        INSERT INTO trigger_test VALUES(NEW.first_name);
    END$$
DELIMITER ;

-- Even more interesting, a conditional on NEW row:
DELIMITER $$
CREATE
    TRIGGER my_trigger BEFORE INSERT
    ON employee
    FOR EACH ROW BEGIN
         IF NEW.sex = 'M' THEN
               INSERT INTO trigger_test VALUES('added male employee');
         ELSEIF NEW.sex = 'F' THEN
               INSERT INTO trigger_test VALUES('added female');
         ELSE
               INSERT INTO trigger_test VALUES('added other employee');
         END IF;
    END$$
DELIMITER ;

-- You can drop triggers too:
drop trigger my_trigger;