mysql存储过程之引发存储过程中的错误条件（SIGNAL和RESIGNAL语句）实例分析

SIGNAL SQLSTATE | condition_name;
SET condition_information_item_name_1 = value_1,
  condition_information_item_name_1 = value_2, etc;

DELIMITER $$
CREATE PROCEDURE AddOrderItem(in orderNo int,
 in productCode varchar(45),
 in qty int,in price double, in lineNo int )
BEGIN
 DECLARE C INT;
 SELECT COUNT(orderNumber) INTO C
 FROM orders 
 WHERE orderNumber = orderNo;
 -- check if orderNumber exists
 IF(C != 1) THEN 
 SIGNAL SQLSTATE '45000'
 SET MESSAGE_TEXT = 'Order No not found in orders table';
 END IF;
 -- more code below
 -- ...
END $$
DELIMITER ;

CALL AddOrderItem(10,'S10_1678',1,95.7,1);

mysql> CALL AddOrderItem(10,'S10_1678',1,95.7,1);
1644 - Order No not found in orders table
mysql>

DELIMITER $$
CREATE PROCEDURE Divide(IN numerator INT, IN denominator INT, OUT result double)
BEGIN
 DECLARE division_by_zero CONDITION FOR SQLSTATE '22012';
 DECLARE CONTINUE HANDLER FOR division_by_zero 
 RESIGNAL SET MESSAGE_TEXT = 'Division by zero / Denominator cannot be zero';
 -- 
 IF denominator = 0 THEN
 SIGNAL division_by_zero;
 ELSE
 SET result := numerator / denominator;
 END IF;
END $$
DELIMITER ;

mysql> CALL Divide(10,0,@result);
1644 - Division by zero / Denominator cannot be zero