CREATE TABLE staff_types (
	id TINYINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
	name VARCHAR(255) UNIQUE
);

ALTER TABLE users DROP COLUMN staff_type;
ALTER TABLE users ADD COLUMN staff_type_id TINYINT DEFAULT NULL;

ALTER TABLE users ADD CONSTRAINT FOREIGN KEY fk_staff_type (staff_type_id) REFERENCES staff_types (id);

INSERT INTO staff_types (id, name) VALUES
	(1, 'Permanent'),
	(2, 'Permanent Part-Time'),
	(3, 'Fixed Term'),
	(4, 'Contractor');
