Group by year query

Question

This is a sample data for a particular employee code 15400. Table name: tab_contr.
EMP_CODE CURR_MONTH DUE_MONTH CONTRIBUTION_AMT
15400 200804 200804 541
15400 200805 200805 541
15400 200806 200806 541
15400 200807 200807 541
15400 200808 200808 541
15400 200809 200809 541
15400 200810 200810 541
15400 200811 200811 541
15400 200812 200812 541
15400 200901 200901 541
15400 200902 200902 541
15400 200903 200903 541
15400 201001 201001 541
Here, using the group by query, I need the following output:
Years Total_Amt
Mar 2008- Feb 2009 sum(contribution_amount for that duration)
Mar 2009- FEb 2010 sum(contribution_amount for that duration)
please help.

Answer 1

with t
as
select 15400 emp_code, 200804 cur_month, 200804 due_month, 541 amt from dual union all
select 15400, 200805, 200805, 541 from dual union all
select 15400, 200806, 200806, 541 from dual union all
select 15400, 200807, 200807, 541 from dual union all
select 15400, 200808, 200808, 541 from dual union all
select 15400, 200809, 200809, 541 from dual union all
select 15400, 200810, 200810, 541 from dual union all
select 15400, 200811, 200811, 541 from dual union all
select 15400, 200812, 200812, 541 from dual union all
select 15400, 200901, 200901, 541 from dual union all
select 15400, 200902, 200902, 541 from dual union all
select 15400, 200903, 200903, 541 from dual union all
select 15400, 201001, 201001, 541 from dual
select emp_code,
       min(cur_year)||'-'||max(cur_year) years,
       sum(amt) amt
  from (
select emp_code,
       extract(year from to_date(cur_month, 'yyyymm')) cur_year,
       extract(month from to_date(cur_month, 'yyyymm')) cur_month,
       amt
  from t)
group by emp_code, cur_year-decode(cur_month, 1, 1, 2, 1, 0)
order by cur_year-decode(cur_month, 1, 1, 2, 1, 0)