Trigger problem i MYSQL

Hejsa.

Jeg er igang med at lave en trigger, men er meget i tvivl om hvordan jeg laver den. Spørgsmålet i min opgave lyder sådan her:

"Create a trigger that removes the season if unused whenever information about when and who produces a product is deleted (i.e., whenever a record is removed from the 'Produces' table, check if there are other records about product being produced for the same season, if not, remove also the corresponding record from the season table)"

Min SQL kode ser sådan ud:

CREATE TABLE IF NOT EXISTS Dvds(
Serial integer NOT NULL,
Name varchar(50),
Year integer,
Genre varchar(50),
Price integer,
PRIMARY KEY (Serial));

CREATE TABLE IF NOT EXISTS Shops(
Id integer NOT NULL,
Name varchar(50),
Address varchar(50),
PRIMARY KEY (Id));

CREATE TABLE IF NOT EXISTS Customers(
CNo integer NOT NULL,
AccNo integer,
Time varchar(50),
PRIMARY KEY (CNo));

CREATE TABLE IF NOT EXISTS ContactPersons(
Id integer NOT NULL,
Name varchar(50),
Phone integer,
PRIMARY KEY (Id));

CREATE TABLE IF NOT EXISTS Seasons(
StartDate date NOT NULL,
EndDate date NOT NULL,
PRIMARY KEY (StartDate,EndDate));

CREATE TABLE IF NOT EXISTS WebShops(
Id integer NOT NULL,
Url varchar(50),
FOREIGN KEY (Id) REFERENCES Shops (Id),
PRIMARY KEY (Id));

CREATE TABLE IF NOT EXISTS Producer(
Id integer NOT NULL,
Address varchar(50),
Name varchar(50),
PRIMARY KEY (Id));

CREATE TABLE IF NOT EXISTS Sold(
Id integer NOT NULL,
CNo integer NOT NULL,
Serial integer NOT NULL,
FOREIGN KEY (Id) REFERENCES Shops (Id),
FOREIGN KEY (CNo) REFERENCES Customers (CNo),
FOREIGN KEY (Serial) REFERENCES Dvds (Serial),
PRIMARY KEY (Id,CNo,Serial));

CREATE TABLE IF NOT EXISTS Has(
Id integer NOT NULL,
Serial integer NOT NULL,
FOREIGN KEY (Id) REFERENCES Shops (Id),
FOREIGN KEY (Serial) REFERENCES Dvds (Serial),
PRIMARY KEY (Id,Serial));

CREATE TABLE IF NOT EXISTS Has2(
Serial integer NOT NULL,
Producer_Id integer NOT NULL,
StartDate date NOT NULL,
EndDate date NOT NULL,
ContactPersons_Id integer NOT NULL,
FOREIGN KEY (Serial) REFERENCES Dvds (Serial),
FOREIGN KEY ( Producer_Id) REFERENCES Producer (Id),
FOREIGN KEY (StartDate) REFERENCES Seasons (StartDate),
FOREIGN KEY (EndDate) REFERENCES Seasons (EndDate),
FOREIGN KEY (ContactPersons_Id) REFERENCES ContactPersons (Id),
PRIMARY KEY (Serial,Producer_Id,StartDate,EndDate,ContactPersons_Id));

Jeg har lavet et par forsøg på en trigger, men kan ikke finde ud af det mere.  Her er mit bud på noget ala det?, eller er jeg forkert på den?

CREATE TRIGGER `Seasons_before_delete` AFTER DELETE ON `Seasons`
FOR EACH ROW
BEGIN
  DELETE FROM Seasons
  WHERE StartDate.ID = old.ID

  DELETE FROM Seasons
  WHERE EndDate.ID = old.ID
END

Håber i kan hjælpe mig i mål?

Med Venlig Hilsen
Mads