if field is json,when query one key from json ,it will help you .
select idfa, appid ,appname , countrycode , get_json_object( field, ‘$.carrier‘ ) from impression_hour where yr = $yr and mt = $mt and dt=$dt and countrycode = ‘SG‘";
refer :
https://docs.microsoft.com/zh-cn/azure/hdinsight/hdinsight-using-json-in-hive
原文：http://www.cnblogs.com/lavin/p/7597511.html