set hive.map.aggr=true;
set hive.groupby.skewindata=false;
set mapred.reduce.tasks=31;

CREATE TABLE dest1(key STRING, c1 INT, c2 STRING) STORED AS TEXTFILE;

EXPLAIN
FROM src
INSERT OVERWRITE TABLE dest1 SELECT substr(src.key,1,1), count(DISTINCT substr(src.value,5)), concat(substr(src.key,1,1),sum(substr(src.value,5))) GROUP BY substr(src.key,1,1);

FROM src
INSERT OVERWRITE TABLE dest1 SELECT substr(src.key,1,1), count(DISTINCT substr(src.value,5)), concat(substr(src.key,1,1),sum(substr(src.value,5))) GROUP BY substr(src.key,1,1);

SELECT dest1.* FROM dest1;