如何从 CURSOR 读取数据 - mysql 存储过程答案

【问题标题】：how to read data from CURSOR - mysql stored procedure如何从 CURSOR 读取数据 - mysql 存储过程
【发布时间】：2018-05-12 05:33:18
【问题描述】：

我已经在 mysql 存储过程中实现了 CURSOR...我在读取游标时遇到了挑战...基本上我想从游标中读取列值并将其存储到变量中..但我得到了变量值为NULL...解决方案是什么...请帮助我..提前致谢...

我的代码如下，

delimiter //

CREATE PROCEDURE placeOrder(IN cartId INT)
BEGIN

   DECLARE countitem INT DEFAULT 0;
   DECLARE productId INT;
   DECLARE quantity INT;
   DECLARE itemDicountAmt DOUBLE DEFAULT 0;
  DECLARE v_finished INT DEFAULT 0;


 DEClARE cart_cursor CURSOR FOR 
 SELECT ProductId, Quantity FROM TBL_SHOPPING_CART_ITEM;

 -- declare NOT FOUND handler
 DECLARE CONTINUE HANDLER 
        FOR NOT FOUND SET v_finished = 1;

 OPEN cart_cursor;

 get_cart: LOOP

 FETCH cart_cursor into productId, quantity;

 IF v_finished = 1 THEN 
 LEAVE get_cart;
 END IF;

 -- build email list
 insert into debugtable select concat('PRODUCT :', productId);
  insert into debugtable select concat('QUANTITY :', quantity);
 END LOOP get_cart;

 CLOSE cart_cursor;

END//

delimiter ;

输出：

tmptable 无效的空

因为我的购物车表中有一条记录...

【问题讨论】：

标签： mysql stored-procedures database-cursor

【解决方案1】：

见C.1 Restrictions on Stored Programs :: Name Conflicts within Stored Routines。

选项 1：

...
/*DEClARE cart_cursor CURSOR FOR 
 SELECT ProductId, Quantity FROM TBL_SHOPPING_CART_ITEM;*/
DEClARE cart_cursor CURSOR FOR 
 SELECT
   TBL_SHOPPING_CART_ITEM.ProductId,
   TBL_SHOPPING_CART_ITEM.Quantity
 FROM TBL_SHOPPING_CART_ITEM;
...

选项 2：

...
/*DECLARE productId INT;
DECLARE quantity INT;*/
DECLARE _productId INT;
DECLARE _quantity INT;
...
/*FETCH cart_cursor into productId, quantity;*/
FETCH cart_cursor into _productId, _quantity;
...
/*insert into debugtable select concat('PRODUCT :', productId);
insert into debugtable select concat('QUANTITY :', quantity);*/
insert into debugtable select concat('PRODUCT :', _productId);
insert into debugtable select concat('QUANTITY :', _quantity);
...

【讨论】：