调试易

-- 我的一个函数
-- 其作用是生成一个可执行的SQL语句，
-- 目的是生成“查询一张表的int类型字段的所有max、min、avg值”的SQL语句的函数：DELIMITER $$CREATE FUNCTION get_tb_numberInfo(v_tb_name varchar(50))
  RETURNS VARCHAR(2000) CHARSET utf8
BEGIN
  DECLARE v_sql varchar(20000);  DECLARE v_column_name varchar(200);
  DECLARE v_column_name_min varchar(200);
  DECLARE v_column_name_max varchar(200);
  DECLARE v_column_name_avg varchar(200);
  DECLARE no_more_departments boolean;  DECLARE get_tbInfo CURSOR FOR
    SELECT column_name FROM information_schema.columns 
     WHERE UPPER(TABLE_NAME)=upper(v_tb_name)
       AND TABLE_SCHEMA=(select database())
       AND DATA_TYPE IN('bigint','int','decimal');  DECLARE CONTINUE HANDLER FOR NOT FOUND SET no_more_departments=1;
  SET no_more_departments=0; 
  SET v_sql := 'SELECT ';
  OPEN get_tbInfo;
  REPEAT
  -- Get get_tbInfo 
  FETCH get_tbInfo INTO v_column_name;
    SET v_column_name_min = concat('min(',v_column_name,') as ',v_column_name,'_min,');
    SET v_column_name_max = concat('max(',v_column_name,') as ',v_column_name,'_max,');
    SET v_column_name_avg = concat('avg(',v_column_name,') as ',v_column_name,'_avg,');
    SET v_sql = concat(v_sql,v_column_name_min,v_column_name_max,v_column_name_avg,'\n');
  UNTIL no_more_departments
  END REPEAT;
  CLOSE get_tbInfo;  SET v_sql = substring(v_sql,1,length(v_sql)-1);
  SET v_sql = concat(v_sql,' from ',v_tb_name,';');  RETURN v_sql;
END;
$$delimiter ;-- 但是：我每次执行后，最后一个字段生成了两次：min、max、avg字段，例如：
mysql> select get_tb_numberInfo('f_union_refer_date_index'); SELECT
min(date_id) as date_id_min,max(date_id) as date_id_max,avg(date_id) as date_id_avg,
min(refer_id) as refer_id_min,max(refer_id) as refer_id_max,avg(refer_id) as refer_id_avg,
min(ip_num) as ip_num_min,max(ip_num) as ip_num_max,avg(ip_num) as ip_num_avg,
min(direct_pv_num) as direct_pv_num_min,max(direct_pv_num) as direct_pv_num_max,avg(direct_pv_num) as direct_pv_num_avg,
min(indirect_pv_num) as indirect_pv_num_min,max(indirect_pv_num) as indirect_pv_num_max,avg(indirect_pv_num) as indirect_pv_num_avg,
min(direct_cv_num) as direct_cv_num_min,max(direct_cv_num) as direct_cv_num_max,avg(direct_cv_num) as direct_cv_num_avg,
min(indirect_cv_num) as indirect_cv_num_min,max(indirect_cv_num) as indirect_cv_num_max,avg(indirect_cv_num) as indirect_cv_num_avg,
min(direct_uv_num) as direct_uv_num_min,max(direct_uv_num) as direct_uv_num_max,avg(direct_uv_num) as direct_uv_num_avg,
min(new_uv_num) as new_uv_num_min,max(new_uv_num) as new_uv_num_max,avg(new_uv_num) as new_uv_num_avg,
min(new_uv_num) as new_uv_num_min,max(new_uv_num) as new_uv_num_max,avg(new_uv_num) as new_uv_num_avg from f_union_refer_date_index;-- 请问是怎么回事儿呢？有什么办法解决不？