mysql光标如何使用

DECLARE cursor_name CURSOR FOR SELECT column1, column2 FROM table_name WHERE condition;

DECLARE user_cursor CURSOR FOR 
SELECT id, name FROM users WHERE age > 18;

DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;

OPEN user_cursor;
<p>read_loop: LOOP
FETCH user_cursor INTO user_id, user_name;
IF done THEN
LE*E read_loop;
END IF;
-- 在这里处理每一行数据，比如插入日志或更新其他表
INSERT INTO processed_users (id, name) VALUES (user_id, user_name);
END LOOP;</p><p>CLOSE user_cursor;</p>

DELIMITER $$
<p>CREATE PROCEDURE ProcessAdultUsers()
BEGIN
DECLARE user_id INT;
DECLARE user_name VARCHAR(50);
DECLARE done INT DEFAULT 0;</p><p>-- 声明光标
DECLARE user_cursor CURSOR FOR 
SELECT id, name FROM users WHERE age > 18;</p><p>-- 设置结束标志
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;</p><p>-- 创建目标表（如果不存在）
CREATE TABLE IF NOT EXISTS processed_users (
id INT, name VARCHAR(50)
);</p><p>-- 打开光标
OPEN user_cursor;</p><p>-- 循环读取
read_loop: LOOP
FETCH user_cursor INTO user_id, user_name;
IF done THEN
LE*E read_loop;
END IF;
INSERT INTO processed_users (id, name) VALUES (user_id, user_name);
END LOOP;</p><p>-- 关闭光标
CLOSE user_cursor;
END$$</p><p>DELIMITER ;</p>

CALL ProcessAdultUsers();