   ADD KEY `staff1` (`staff1`),
   ADD KEY `staff2` (`staff2`),
   ADD KEY `staff3` (`staff3`),
-  ADD KEY `staff4` (`staff4`);
+  ADD KEY `staff4` (`staff4`),
+  ADD CONSTRAINT `staff4FK` FOREIGN KEY (`staff4`) REFERENCES `users` (`username`) ON UPDATE CASCADE,
+  ADD CONSTRAINT `staff1FK` FOREIGN KEY (`staff1`) REFERENCES `users` (`username`) ON UPDATE CASCADE,
+  ADD CONSTRAINT `staff2FK` FOREIGN KEY (`staff2`) REFERENCES `users` (`username`) ON UPDATE CASCADE,
+  ADD CONSTRAINT `staff3FK` FOREIGN KEY (`staff3`) REFERENCES `users` (`username`) ON UPDATE CASCADE;
 
 /* create new user
  change address and password to desired values */
 create user 'staff'@'192.168.1.%' identified by 'password';
 
 /* change address to desired value */
-grant select, insert, delete, alter on staff.* to 'staff'@'192.168.1.%';
+grant select, insert, delete, alter on staff.* to 'staff'@'192.168.1.%';
  `lifeguard` tinyint(1) DEFAULT NULL,
  `lts` tinyint(1) DEFAULT NULL,
  `gym` tinyint(1) DEFAULT NULL,
  PRIMARY KEY (ID)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

INSERT INTO `location` (`ID`, `Location`, `lifeguard`, `lts`, `gym`) VALUES (1, 'None', 1, 1, 1);


) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

ALTER TABLE `availability`
ADD KEY `username` (`username`),
ADD CONSTRAINT `usernameFK` FOREIGN KEY (`username`) REFERENCES `users` (`username`) ON UPDATE CASCADE;

/* create ISC table */
CREATE TABLE `isc` (
  `ID` int(4) NOT NULL,
  `shift_date` date NOT NULL,
  `start_time` time NOT NULL,
