Interchange values from one row with another row

Question

Dear Oracle Guru's
While Migrating data from legacy system, there was a confusion and data in two columns got jumbled
Ex The data should be like this
Custcode leaseno
1034 A234
1035 A235
1036 A236
whereas the table has data like this
Custcode leaseno
1034 A235
1035 A234
1036 A237
1037 A236
How do we swap values between two rows
Kindly guide me on this
With Warm Regards
ssr

Answer 1

>
Ex The data should be like this
Custcode leaseno
1034 A234
1035 A235
1036 A236
whereas the table has data like this
Custcode leaseno
1034 A235
1035 A234
1036 A237
1037 A236
How do we swap values between two rows And now, time for yet another guess... ;)
My guess is that your migration program interchanged "leaseno" value in pairs from the top - the top being the least value of "custcode".
So, the "leaseno" values of Row 1 and Row 2 were swapped.
The "leaseno" values of Row 3 and Row 4 were swapped.
And so on.
Which also means that if the total number of rows in your table is even, then the swap would be "complete". Otherwise, the last row would be left out. I don't know what you want to do with that.
test@XE>
test@XE> select * from t;
  CUSTCODE LEAS
      1034 A235
      1035 A234  <= you want to swap A235 and A234
      1036 A237
      1037 A236  <= you want to swap A237 and A236
      1038 A238  <= let's leave it hanging there...
5 rows selected.
test@XE>
test@XE> And of course, swapping from "top to bottom" means swapping from the least to highest value of "custcode".
Here's the SELECT statement for that -
test@XE>
test@XE> -- show the records in the table t
test@XE>
test@XE> select * from t;
  CUSTCODE LEASENO
      1034 A235
      1035 A234
      1036 A237
      1037 A236
      1038 A238
5 rows selected.
test@XE>
test@XE> -- the SELECT statement for swapping leaseno values
test@XE>
test@XE> @test7a
test@XE> --
test@XE> select custcode,
  2         leaseno,
  3         case
  4           when mod(row_number() over (order by custcode),2) = 1 and
  5                lead(leaseno) over (order by custcode) is null
  6           then leaseno
  7           when mod(row_number() over (order by custcode),2) = 1
  8           then lead(leaseno) over (order by custcode)
  9           else lag(leaseno) over (order by custcode)
10         end as new_leaseno
11  from t;
  CUSTCODE LEASENO NEW_LEASENO
      1034 A235    A234
      1035 A234    A235
      1036 A237    A236
      1037 A236    A237
      1038 A238    A238
5 rows selected.
test@XE>
test@XE> And here's the update statement -
test@XE>
test@XE> -- the UPDATE statement for updating leaseno values in pairs from the top
test@XE>
test@XE> @test7b
test@XE> --
test@XE> update t t1
  2  set t1.leaseno = (
  3    select new_leaseno
  4    from (
  5      select custcode,
  6             leaseno,
  7             case
  8             when mod(row_number() over (order by custcode),2) = 1 and
  9                  lead(leaseno) over (order by custcode) is null
10             then leaseno
11             when mod(row_number() over (order by custcode),2) = 1
12             then lead(leaseno) over (order by custcode)
13             else lag(leaseno) over (order by custcode)
14           end as new_leaseno
15      from t
16    ) t2
17    where t2.custcode = t1.custcode
18  );
5 rows updated.
test@XE>
test@XE>
test@XE> select * from t;
  CUSTCODE LEASENO
      1034 A234
      1035 A235
      1036 A236
      1037 A237
      1038 A238
5 rows selected.
test@XE>
test@XE> HTH,
isotope