Need help in SQL , Subtract column based on the condition in the Row

Question

Hi all ,
I’m new to Sql Queries; I have a requirement which involves Sql query,
Can anyone tell the How to proceed or provide me Sql
Here goes the requirement
Current Table
ID |-|Month|-|Data
1|-|Jan-10|-|10.00
2|-|Feb-10|-|20.00
3|-|Mar-10|-|30.00
4|-|Apr-10|-|50.00
5|-|May-10|-|60.00
6|-|Jun-10|-|70.00
7|-|Jul-10|-|100.00
8|-|Aug-10|-|110.00
9|-|Sep-10|-|120.00
10|-|Oct-10|-|140.00
11|-|Nov-10|-|150.00
12|-|Dec-10|-|170.00
13|-|Jan-09|-|180.67
14|-|Feb-09|-|194.67
15|-|Mar-09|-|208.67
16|-|Apr-09|-|222.67
Format needed
ID |-|Month|-|Data|-|Base on this condition
1|-|Jan-10|-|10.00|-|Jan 10
2|-|Feb-10|-|10.00|-|Feb10-Jan10
3|-|Mar-10|-|10.00|-|Mar10 - Feb10
4|-|Apr-10|-|20.00|-|Apr10 - Mar10
5|-|May-10|-|10.00|-|May10 - Apr10
6|-|Jun-10|-|10.00|-|Jun10 - May10
7|-|Jul-10|-|30.00|-|Jul10 - Aug10
8|-|Aug-10|-|10.00|-|Aug10 - Jul10
9|-|Sep-10|-|10.00|-|Sep10 -Aug10
10|-|Oct-10|-|20.00|-|Oct10 -Sep10
11|-|Nov-10|-|10.00|-|Nov10 - Oct10
12|-|Dec-10|-|20.00|-|Dec10 - Nov10
13|-|Jan-09|-|10.67|-|Jan 09
14|-|Feb-09|-|14.00|-|Feb09-Jan09
15|-|Mar-09|-|14.00|-|Mar09 - Feb09
16|-|Apr-09|-|14.00|-|Apr09 - Mar09
Thanks in advance
Astle

Answer 1

Welcome to the forum!
this?
select id
     , mon
     , data
     , data - lag (data, 1, 0) over (partition by trunc (mon, 'yyyy')
               order by mon)
  from test
order by idas in
SQL> with test as
  2  (
  3  select 1 id ,to_date ('Jan-10', 'Mon-rr') mon,10.00 data from dual union all
  4  select 2,to_date ('Feb-10', 'Mon-rr'),20.00 data from dual union all
  5  select 3,to_date ('Mar-10', 'Mon-rr'),30.00 data from dual union all
  6  select 4,to_date ('Apr-10', 'Mon-rr'),50.00 data from dual union all
  7  select 5,to_date ('May-10', 'Mon-rr'),60.00 data from dual union all
  8  select 6,to_date ('Jun-10', 'Mon-rr'),70.00 data from dual union all
  9  select 7,to_date ('Jul-10', 'Mon-rr'),100.00 data from dual union all
10  select 8,to_date ('Aug-10', 'Mon-rr'),110.00 data from dual union all
11  select 9,to_date ('Sep-10', 'Mon-rr'),120.00 data from dual union all
12  select 10,to_date ('Oct-10', 'Mon-rr'),140.00 data from dual union all
13  select 11,to_date ('Nov-10', 'Mon-rr'),150.00 data from dual union all
14  select 12,to_date ('Dec-10', 'Mon-rr'),170.00 data from dual union all
15  select 13,to_date ('Jan-09', 'Mon-rr'),180.67 data from dual union all
16  select 14,to_date ('Feb-09', 'Mon-rr'),194.67 data from dual union all
17  select 15,to_date ('Mar-09', 'Mon-rr'),208.67 data from dual union all
18  select 16,to_date ('Apr-09', 'Mon-rr'),222.67 data from dual
19  )
20  select id
21       , mon
22       , data
23       , data - lag (data, 1, 0) over (partition by trunc (mon, 'yyyy')
24                 order by mon)
25    from test
26   order by id
27  ;
        ID MON               DATA DATA-LAG(DATA,1,0)OVER(PARTITI
         1 1-1-2010            10                             10
         2 1-2-2010            20                             10
         3 1-3-2010            30                             10
         4 1-4-2010            50                             20
         5 1-5-2010            60                             10
         6 1-6-2010            70                             10
         7 1-7-2010           100                             30
         8 1-8-2010           110                             10
         9 1-9-2010           120                             10
        10 1-10-2010          140                             20
        11 1-11-2010          150                             10
        12 1-12-2010          170                             20
        13 1-1-2009        180,67                         180,67
        14 1-2-2009        194,67                             14
        15 1-3-2009        208,67                             14
        16 1-4-2009        222,67                             14
16 rows selected