如何在mysql游标循环中只插入一次

DELIMITER //

CREATE PROCEDURE insertOnce()
BEGIN
    DECLARE done INT DEFAULT FALSE;
    DECLARE col_name VARCHAR(255);
    
    DECLARE cur CURSOR FOR SELECT column_name FROM table_name;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
    
    OPEN cur;
    
    read_loop: LOOP
        FETCH cur INTO col_name;
        
        IF done THEN
            LEAVE read_loop;
        END IF;
        
        -- 在这里执行插入操作
        INSERT INTO another_table (column_name) VALUES (col_name);
        
        -- 设置标志变量，确保只插入一次
        SET done = TRUE;
    END LOOP;
    
    CLOSE cur;
END//

DELIMITER ;

CALL insertOnce();