Adding sequence number to existing rows based on ID and Date in PLSQL Oracle

All we need is an easy explanation of the problem, so here it is.

I want to add a sequence number (SEQNO) based on their REFNO and STARTD.

Old Table

New Table

How to solve :

I know you bored from this bug, So we are here to help you! Take a deep breath and look at the explanation of your problem. We have many solutions to this problem, But we recommend you to use the first method because it is tested & true method that will 100% work for you.

Method 1

begin
 For r in (Select t.*,
  row_number() over (partition by refno order by startd) seqno
  From my_table t
  Order by refno, startd) loop
   Update my_table
     set seqno = r.seqno
     where refno = r.refno
       and startd = r.startd;
 End loop;
 Commit;
End;

See http://sqlfiddle.com/#!4/484b3/5 for example of row_number.
This pl/sql anonymous block can only handle a limited number of records.

Method 2

You can use MERGE:

merge 
  into tableX t
  using 
  ( select t.*, 
           row_number() over (partition by refno order by startd) as rn
    from tableX t
  ) r
  on ( t.refno = r.refno and t.startd = r.startd )
when matched
  then update
  set
   seqno = r.rn ;

Test in dbfiddle.uk.

(I assume that the PK is (refno, startd)

Note: Use and implement method 1 because this method fully tested our system.
Thank you 🙂

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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