MYSQL游标循环，运行一个额外的一轮，为什么呢？(MYSQL cursor loop, runs

我通过在MySQL存储过程中设置一个游标结果循环。 我现在面临的一个问题是环路始终运行彻底的最后一条记录的两倍。 这里是我的代码，

BEGIN
DECLARE not_found_creadit INT DEFAULT 0;

DECLARE cur_credit CURSOR FOR 
SELECT customer_id, amount, status, user_type, employee, note FROM credit WHERE status = 'approved' AND customer_id = int_cust_id;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET not_found_creadit = 1;
OPEN cur_credit;
  SET not_found_creadit = 0;
  credit_loop : LOOP 
      IF not_found_creadit THEN
        CLOSE cur_credit;
        LEAVE credit_loop;
      END IF;
      FETCH cur_credit INTO vc_customer, dec_amount, vc_status, vc_user_type, vc_emp, vc_note;
      SELECT vc_customer, dec_amount, vc_status, vc_user_type, vc_emp, vc_note;
      ......
      ......
  END LOOP;
END;

也就是说，如果我有3条记录，循环运行的4倍，如果是10条循环运行11次，等等。任何想法发生了什么吗？

Answer 1:

处理程序，这台not_found_creadit = 1 ，就会引发FETCH没有返回行，但在执行前要检查它的价值FETCH ，所以你的循环的主体将执行一个额外的时间，当FETCH失败，则循环退出循环下一轮迭代的开始。

重新安排你的代码后，立即检查您的变量的值FETCH ：

credit_loop : LOOP 
    FETCH cur_credit INTO vc_customer, dec_amount, vc_status, vc_user_type, vc_emp, vc_note;
    IF not_found_creadit THEN
        CLOSE cur_credit;
        LEAVE credit_loop;
    END IF;
    SELECT vc_customer, dec_amount, vc_status, vc_user_type, vc_emp, vc_note;
    ......
    ......
END LOOP;

另外，还要考虑纠正你的变量的拼写not_found_credit

Answer 2:

BECAUSE我写DEFAULT（我不知道你在表信用），你必须正确类型。 结束。如果U创建表不是Temptable使用

TRUNCATE TempTable;

请重写例子

CREATE CREATE TEMPORARY TABLE TempTable (`Id` int(11) NOT NULL auto_increment,
  `customer_id` int(11) NOT NULL,
  `amount` int(11) NOT NULL,
  `status` varchar(1000) NOT NULL,
  `user_type` int(11) NOT NULL default '0',
  `employee` varchar(1000) NOT NULL,
  PRIMARY KEY  (`customer_id`),
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_polish_ci AUTO_INCREMENT=1 ;");

ofcourse类型是坏:)

 DELIMITER $$
    DROP PROCEDURE IF EXISTS CursorX $$
    CREATE PROCEDURE `CursorX`()
    BEGIN    
            DECLARE xCustomerId int(11);  
            DECLARE xStatus   int(11);
            DECLARE xUserType  varchar(255);
            DECLARE xEmployee  varchar(255);
            DECLARE xNote varchar(255);  
            DECLARE i int(11);
            DECLARE recordNotFound INTEGER DEFAULT 0;
            DECLARE cur_credit CURSOR FOR SELECT customer_id, amount, status, user_type, employee, note FROM credit WHERE status = 'approved' AND customer_id = int_cust_id;
            DECLARE CONTINUE HANDLER FOR NOT FOUND SET recordNotFound = 1;

            DROP TEMPORARY TABLE IF EXISTS TempTable;
            CREATE TEMPORARY TABLE TempTable AS(SELECT * FROM credit);

            OPEN cur_credit;
            set not_found_creadit = 0;
            credit_loop: LOOP
            SET i = i +1;
                FETCH cur_credit INTO xCustomerId,xStatus,xUserType,xEmployee,xNote;
                IF not_found_creadit THEN
                    LEAVE credit_loop;
                 END IF;
            END LOOP credit_loop;
            CLOSE cur_credit;
    select * FROM TempTable;

    END $$

文章来源: MYSQL cursor loop, runs one extra round, why?