Hive/Impala translator - select distinct and gorup by is not supported in one query

Hive and Impala do not support combination of SELECT DISTINCT and GROUP BY in one SQL query.

Messages of exceptions:
Impala - cannot combine SELECT DISTINCT with aggregate functions or GROUP BY
Hive - SELECT DISTINCT and GROUP BY can not be in the same query.

DDL:

CREATE VIEW Agg2 (StringNum string)
  AS SELECT BQT1.SmallA.StringNum FROM BQT1.SmallA GROUP BY BQT1.SmallA.StringNum HAVING BQT1.SmallA.StringNum = '1';

Query:

SELECT DISTINCT StringNum FROM VQT.Agg2