Changing the order sequence

Question

Hello,
i have a table test contains these data.
group sequence value
1 1 100
1 2 200
1 3 300
1 4 400
1 5 500
1 6 600
Now i want to change the sequence. ie, eg change the sequence of 2nd record to 5th.
ie moving the 2nd record to 5th and re arrange the sequence. so the records get rearranged
with new sequence.
3 becomes ==> 2
4 becomes ==> 3
5 becomes ==> 4
so the records should looks like
1 1 100
1 2 300
1 3 400
1 4 500
1 5 200 --> 2nd record moved to 5th
1 6 600
how can i achieve this?

Answer 1

create table TestTable AS
SELECT 1 group_id, 1 seq, 100 val FROM DUAL UNION
SELECT 1 group_id, 2 seq, 200 val FROM DUAL UNION
SELECT 1 group_id, 3 seq, 300 val FROM DUAL UNION
SELECT 1 group_id, 4 seq, 400 val FROM DUAL UNION
SELECT 1 group_id, 5 seq, 500 val FROM DUAL UNION
SELECT 1 group_id, 6 seq, 600 val FROM DUAL;"excahnge 2 and 5" is easy.
select group_id,seq,
case when seq = 2 then max(decode(seq,5,val)) over()
     when seq = 5 then max(decode(seq,2,val)) over()
     else val end as seq
from TestTable;"excahnge 2 to 5" is this solution.
This solution is used for ReverseSort.
select group_id,seq,val as OldVal,RevSeq - seq as a,abs(RevSeq - seq) as b,
case when seq between 2 and 5
      and RevSeq - seq  > 0 then Lead(val,abs(RevSeq - seq)) over(order by seq)
     when seq between 2 and 5
      and RevSeq - seq <= 0 then Lag (val,abs(RevSeq - seq)) over(order by seq)
else val end as newVal
from (select group_id,seq,val,
      Row_Number() over(order by seq desc) RevSeq
      from TestTable)
order by seq;update is complex.
update TestTable a set
val = (select newVal
         from (select Row_ID,
                case when seq between 2 and 5
                      and RevSeq - seq  > 0 then Lead(val,abs(RevSeq - seq)) over(order by seq)
                     when seq between 2 and 5
                      and RevSeq - seq <= 0 then Lag (val,abs(RevSeq - seq)) over(order by seq)
                     else val end as newVal
                 from (select seq,val,
                       RowID as Row_ID,
                       Row_Number() over(order by seq desc) as RevSeq
                       from TestTable)) b
        where b.Row_ID = a.RowID)
where seq between 2 and 5;