How to fix ERROR 1407: Bad SQLSTATE in MySQL

-- TOO SHORT (3 chars)
DECLARE my_condition CONDITION FOR SQLSTATE "123";

-- TOO LONG (6 chars)
DECLARE my_condition CONDITION FOR SQLSTATE "123456";

-- CORRECT (5 chars)
DECLARE my_condition CONDITION FOR SQLSTATE "45000";

-- WRONG: "00" indicates success
DECLARE my_condition CONDITION FOR SQLSTATE "00123";

-- CORRECT: Use "45000" for user-defined exceptions
DECLARE my_condition CONDITION FOR SQLSTATE "45000";

DELIMITER //

CREATE PROCEDURE validate_age(IN p_age INT)
BEGIN
  DECLARE invalid_age CONDITION FOR SQLSTATE "45000";
  
  IF p_age < 0 THEN
    SIGNAL invalid_age SET MESSAGE_TEXT = "Age cannot be negative";
  END IF;
END //

DELIMITER ;

-- WRONG: Will cause ERROR 1407
SIGNAL SQLSTATE "00000" SET MESSAGE_TEXT = "Error";

-- CORRECT: Use valid SQLSTATE
SIGNAL SQLSTATE "45000" SET MESSAGE_TEXT = "An error occurred";

CREATE TRIGGER validate_insert BEFORE INSERT ON users
FOR EACH ROW
BEGIN
  IF NEW.email IS NULL THEN
    SIGNAL SQLSTATE "45000" SET MESSAGE_TEXT = "Email cannot be null";
  END IF;
END;

DELIMITER //

CREATE PROCEDURE process_order(IN p_order_id INT)
BEGIN
  -- Declare conditions properly
  DECLARE invalid_order CONDITION FOR SQLSTATE "45001";
  DECLARE processing_error CONDITION FOR SQLSTATE "45002";
  
  -- Use them in handlers
  DECLARE EXIT HANDLER FOR 1451
  BEGIN
    SIGNAL invalid_order SET MESSAGE_TEXT = "Cannot process order with related records";
  END;
  
  -- Procedure logic here
END //

DELIMITER ;