Trouble with SQL 1005 errors (errno 150) - mysql

Question

I, like many others, am struggling with the infamous errno 150 in mySQL. I know it has to do with foreign keys, and I know there are already many questions about this issue, but after spending a substantial amount of time searching for a solution I am yet to find one that fits my specific case. Almost every error has been worked out of this travel database, but this final one arises upon trying to create a table entitled leg. I will post below the tables that are involved with this.
CREATE TABLE ticket(
id int UNSIGNED NOT NULL,
passenger_id int UNSIGNED,
trip_id int UNSIGNED,
leg_no int UNSIGNED,
purchased_on datetime,
reservation_date date,
PRIMARY KEY(id),
CONSTRAINT fk_ticket_passenger_id_passenger FOREIGN KEY
(passenger_id) REFERENCES passenger(id),
CONSTRAINT fk_ticket_trip_id_trip FOREIGN KEY
(trip_id) REFERENCES trip(id),
CONSTRAINT fk_ticket_leg_no_leg FOREIGN KEY
(leg_no) REFERENCES leg(leg_no));
CREATE TABLE trip(
id int UNSIGNED NOT NULL,
number_of_legs int UNSIGNED,
PRIMARY KEY(id));
CREATE TABLE leg(
trip_id int UNSIGNED NOT NULL,
leg_no int UNSIGNED NOT NULL,
origin_id int UNSIGNED,
destination_id int UNSIGNED,
depart_time time,
arrive_time time,
vdesignation varchar(255),
price decimal(13,2),
PRIMARY KEY(trip_id, leg_no),
CONSTRAINT fk_leg_trip_id_trip FOREIGN KEY
(trip_id) REFERENCES trip(id),
CONSTRAINT fk_leg_vdesignation_vehicle FOREIGN KEY
(vdesignation) REFERENCES vehicle(designation),
CONSTRAINT fk_leg_origin_id_island FOREIGN KEY
(origin_id) REFERENCES island(id),
CONSTRAINT fk_leg_destination_id_island FOREIGN KEY
(destination_id) REFERENCES island(id));
CREATE TABLE vehicle(
designation varchar(255) NOT NULL,
vtype varchar(255),
capacity int UNSIGNED,
PRIMARY KEY(designation));
CREATE TABLE island(
id int UNSIGNED NOT NULL,
iname varchar(255),
can_fly tinyint UNSIGNED,
PRIMARY KEY(id));
I am aware that this question gets asked a lot, and I'm sure it gets old, I will be incredibly appreciative of any advice that you may have for me. I've searched quite thoroughly for the solution and cannot seem to figure it out. Thanks ahead of time for any info you can give me!
EDIT: Here is the specific warning info for the error:
*************************** 1. row ***************************
Level: Error
Code: 1005
Message: Can't create table 'travel.leg' (errno: 150)
1 row in set (0.04 sec)
EDIT 2: Added the vehicle table in response to the first answer, because somehow I forgot to add it in the first place.

Answer 1

I see two potential problems with the foreign keys in your leg table:
1. The first problem is with the fk_leg_vdesignation foreign key
CONSTRAINT fk_leg_vdesignation_vehicle FOREIGN KEY (vdesignation)
REFERENCES vehicle(designation)
You never showed us the vehicle table, so we can't verify that the designation column there as the same type as leg.vdesignation, which is varchar(255). If the types don't match, or if vehicle.designation does not exist, you should get the 150 error you are seeing.
2. The following two foreign keys in leg both appear to be referencing the same column in the island table:
CONSTRAINT fk_leg_origin_id_island FOREIGN KEY (origin_id) REFERENCES island(id)
CONSTRAINT fk_leg_destination_id_island FOREIGN KEY (destination_id) REFERENCES island(id)
I don't see the point of having both of them. Furthermore, the type of leg.origin_id and leg.destination_id is int UNSIGNED, while the type of the foreign column island.id is int UNSIGNED NOT NULL. Since the types are not exactly the same, this could be causing the error 150.

Answer 2

I ended up figuring it out via a sudden burst of intuition. The issue actually came from the ticket table. To resolve the issue, I combined the final two foreign keys of the table. This means that I changed my constraints from this:
CONSTRAINT fk_ticket_trip_id_trip FOREIGN KEY
(trip_id) REFERENCES trip(id),
CONSTRAINT fk_ticket_leg_no_leg FOREIGN KEY
(leg_no) REFERENCES leg(leg_no));
To this:
CONSTRAINT fk_ticket_leg_no_leg FOREIGN KEY
(trip_id, leg_no) REFERENCES leg(trip_id, leg_no));
My understanding of what went wrong is that a foreign key is supposed to reference a primary key of another table. When the second of the two foreign keys referred to leg.leg_no, it was only referring to part of the key. leg.leg_no is a prime attribute from the primary key, but on its own cannot identify a particular row of the table, so it will not function properly as a foreign key reference.
Thank you anyway to Tim for helping me! Without your comment about having two foreign keys refer to the same key, I may never have thought of this.