MySQL 笔记（六）游标练习两道

意义不明的两道练习，留着备用。

感觉不好写，而且难以调试。。不知道以后会不会有实际的应用场景。

1、利用游标查找所有女业务员的基本情况

DROP PROCEDURE IF EXISTS show_female_details;
DELIMITER //
CREATE PROCEDURE show_female_details()
BEGIN
    -- 用于保存 FETCH 结果的变量
    DECLARE employee_no VARCHAR(8);
    DECLARE employee_name VARCHAR(10);
    DECLARE sex CHAR(1);
    DECLARE birthday DATE;
    DECLARE address VARCHAR(50);
    DECLARE telephone VARCHAR(20);
    DECLARE hiredate DATE;
    DECLARE department VARCHAR(30);
    DECLARE headship VARCHAR(10);
    DECLARE salary DECIMAL(8,2);
    DECLARE cnt INT DEFAULT 0;
    -- 循环变量
    DECLARE i INT DEFAULT 0;
    -- 声明游标
    DECLARE employee_details CURSOR FOR SELECT * FROM employee;
    OPEN employee_details;
    -- ERROR 1337 (42000): Variable or condition declaration after cursor or handler declaration
    -- employee 表的元组数
    SELECT COUNT(*) FROM employee INTO cnt; -- 如果放在游标声明之前将报错。
    
    WHILE i < cnt DO -- 意外发现：TAB控制缩进报错，空格缩进不报错
     SET i:=i+1;
     FETCH employee_details
     INTO employee_no, employee_name, sex, birthday, address, telephone, hiredate, department, headship, salary;
     IF sex = 'F' THEN
      SELECT employee_no, employee_name, sex, birthday, address, telephone, hiredate, department, headship, salary;
     END IF;
    END WHILE;
END // 
DELIMITER ;
CALL show_female_details();
-- imooc 为什么使用存储过程 补充

2、利用游标修改orderMaster表中的Ordersum的值

DROP PROCEDURE IF EXISTS cal_sum;
DELIMITER //
CREATE PROCEDURE cal_sum()
BEGIN
    -- 用于保存 FETCH 结果的变量
    DECLARE order_num VARCHAR(12);
    
    DECLARE done INT DEFAULT 0;
    -- 当抛出 not find 的时候把 done 改成 true
    -- 什么时候抛出 not find 呢？在游标 FETCH 不到数据的时候
    DECLARE order_nos CURSOR FOR SELECT order_no FROM order_master;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;  
    -- ERROR 1338 (42000): Cursor declaration after handler declaration
    -- ERROR 1337 (42000): Variable or condition declaration after cursor or handler declaration
    -- 总之 cursor 的声明位置很苛刻。。。
    
    OPEN order_nos;
    
    WHILE (NOT done) DO
     -- SELECT VERSION();
     -- SET done:=1; -- 测试专用
     FETCH order_nos INTO order_num;
     UPDATE order_master 
     SET order_sum = (
      SELECT SUM(quantity*price)
      FROM order_detail
      GROUP BY order_detail.order_no
      HAVING order_detail.order_no = order_num
     )
     WHERE order_master.order_no = order_num;
    END WHILE;
END // 
DELIMITER ;
CALL cal_sum();

MySQL 笔记（六）游标练习两道

猜你喜欢