Two Cursors in a procedure

Question

I am working on procedure, Please give ideas where i can develop this logic more meaning and easy
the logic is as follows
Table1 is having same Id's ABC having same seq number 100 as per legacy data (This is wrong entry in legacy data)
ID     --    Seqnum
ABC --     100
ABC --     100
I created a table2 where it will have max seqnum from legacy for this ID's for example ABC
ID  -- Max seqnum
ABC --500
In my procedure I will have two cursors
First cursor will be have Table1 detail
Second Cursor will have Table2 Details
In above ex the table will have the first record should be unchanged i.e.,
ABC --     100 --100
but second record will change to
ABC --     100 -- 501(This next value of the max seq number from table 2/Cursor 2)
I have to create third column which will hold the next seqnumber for that ID ABC
I should load both records changing the seqnumber so I will not have any duplicate records for same ID.
So final records will look like
ID            Seq#       Final_Seq#
ABC --     100 --     100
ABC --     100 --      501
Thanks in advance.

Answer 1

Adjusted accordingly to the message above
with
data_tab as
(select 'ABC' id,100 seq from dual union all
select 'ABC',100 from dual union all
select 'ABC',100 from dual union all
select 'BCD',110 from dual union all
select 'CDE',120 from dual union all
select 'CDE',120 from dual union all
select 'DEF',130 from dual union all
select 'EFG',140 from dual union all
select 'EFG',140 from dual union all
select 'EFG',140 from dual union all
select 'EFG',240 from dual union all
select 'EFG',240 from dual union all
select 'FGH',150 from dual
max_nums as
(select 'ABC' id,200 max_num from dual union all
select 'BCD',300 from dual union all
select 'CDE',400 from dual union all
select 'DEF',500 from dual union all
-- select 'EFG',600 from dual union all
select 'FGH',700 from dual
select d.id,d.seq,row_number() over (partition by d.id,d.seq order by null) rn,m.max_num,
       case when row_number() over (partition by d.id,d.seq order by null) = 1
            then d.seq
            else nvl(m.max_num,d.seq) + row_number() over (partition by d.id,d.seq order by null) - 1
       end new_seq
  from data_tab d,
       max_nums m
where d.id = m.id(+)
ID
SEQ
RN
MAX_NUM
NEW_SEQ
ABC
100
1
200
100
ABC
100
2
200
201
ABC
100
3
200
202
BCD
110
1
300
110
CDE
120
1
400
120
CDE
120
2
400
401
DEF
130
1
500
130
EFG
140
1
140
EFG
140
2
141
EFG
140
3
142
EFG
240
1
240
EFG
240
2
241
FGH
150
1
700
150