user_ids=Myshixun.find_by_sql("select distinct(user_id) from myshixuns where created_at between #{start_time} and #{end_time} and shixun_id in (select shixun_id from stage_shixuns
user_ids=Myshixun.find_by_sql("select distinct(user_id) from myshixuns where created_at between '#{start_time}' and '#{end_time}' and shixun_id in (select shixun_id from stage_shixuns