ALTER TABLE `vn2008`.`Tickets_dits` 
DROP FOREIGN KEY `fgkey3`;
ALTER TABLE `vn2008`.`Tickets_dits` 
CHANGE COLUMN `Id_Trabajador` `Id_Trabajador` INT(11) NULL DEFAULT NULL ;
ALTER TABLE `vn2008`.`Tickets_dits` 
ADD CONSTRAINT `fgkey3`
  FOREIGN KEY (`Id_Trabajador`)
  REFERENCES `vn2008`.`Trabajadores` (`Id_Trabajador`)
  ON DELETE NO ACTION
  ON UPDATE CASCADE;