mysql游标索引

-- 创建表
CREATE TABLE employees (
    id INT PRIMARY KEY,
    name VARCHAR(100),
    age INT
);

-- 插入数据
INSERT INTO employees (id, name, age) VALUES (1, 'Alice', 30);
INSERT INTO employees (id, name, age) VALUES (2, 'Bob', 25);
INSERT INTO employees (id, name, age) VALUES (3, 'Charlie', 35);

-- 创建索引
CREATE INDEX idx_age ON employees(age);

-- 使用显式游标
DELIMITER $$
CREATE PROCEDURE process_employees()
BEGIN
    DECLARE done INT DEFAULT FALSE;
    DECLARE emp_id INT;
    DECLARE emp_name VARCHAR(100);
    DECLARE emp_age INT;
    DECLARE cur CURSOR FOR SELECT id, name, age FROM employees WHERE age > 25;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

    OPEN cur;

    read_loop: LOOP
        FETCH cur INTO emp_id, emp_name, emp_age;
        IF done THEN
            LEAVE read_loop;
        END IF;
        -- 处理每一行数据
        SELECT CONCAT('ID: ', emp_id, ', Name: ', emp_name, ', Age: ', emp_age);
    END LOOP;

    CLOSE cur;
END$$
DELIMITER ;

-- 调用存储过程
CALL process_employees();