mybatis 如果返回值为空，设0

 SELECT CASE WHEN s1.online_status IS NOT NULL AND TRIM(s1.online_status)!='' THEN s1.online_status ELSE 0 END online_status  FROM server_config  c  LEFT JOIN  `cur_data_original` d on d.`key` = c.`key` left join server_status s1  SELECT CASE WHEN s1.online_status IS NOT NULL