group by and aggregate functions in queries for building reports

Summary

group by and aggregate functions in queries for building reports

Content

Question: How to use aggregate functions and group clause in rest queries?
We don't want to use aggregate at object level which requires parent.
               
For example How to implement below mentioned query in VBCS rest call
SELECT response_status, SUM (r_unit) FROM emp_map GROUP BY response_status;

 * We need group by  and aggregate functions in queries for building reports