MySql存储过程：保留每月末数据及最新一版数据

CREATE PROCEDURE `p_preserve_his`(in months int)
BEGIN
    Declare lastMonth date;
    Declare lastdt int;
    Declare statisdate int;
    DECLARE i int;
    DECLARE loop_index int DEFAULT 0;
    DECLARE done boolean DEFAULT FALSE;
    DECLARE need_delete boolean DEFAULT TRUE;
    DECLARE cur CURSOR FOR select distinct dt from $table_name order by dt DESC;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
    
    OPEN cur;
    read_loop: LOOP
  
        FETCH next from cur INTO statisdate;
        #结束循环
        IF done THEN
          LEAVE read_loop;
        END IF;