Replacing varchar2 with bigger data type in oracle

Question

I am using oracle verion 10. There is stored procedure in PL/SQL using varchar2 variable. The code is constantly appending the varchar2 variable. When the varchar2 variable size exceeds 32767, it cannot append any more value. Now I want to change the data type to long or clob(in order to accomodate more characters), it does not work. How to modify the code here to have the same appending functionality with clob or long?

sample appending x:= x || 'mydata';

Answer 1

The long datatype is deprecated; if you can you should seriously consider migrating your long column to a clob.

If you were working with a clob you could append past the 32k varchar2 limit like this:

declare
  l_clob clob;
begin
  dbms_lob.createtemporary(l_clob, true);
  dbms_lob.open(l_clob, dbms_lob.lob_readwrite);
  dbms_lob.writeappend(l_clob, 4, '1234');
  for i in 1..10000 loop
    dbms_lob.writeappend(l_clob, 5, '.5678');
  end loop;
  dbms_output.put_line('CLOB length: ' || length(l_clob));
  dbms_lob.close(l_clob);
  dbms_lob.freetemporary(l_clob);    end;
/

CLOB length: 50004

You can append to a long with the concatenate operator ||, but as you've seen already, only up to 32k. There is no easy way to handle long values above that within PL/SQL. You might be able to do soemthing with dbms_sql but it's really not going to be worth the effort if there is any possiblility of switching the table column to a clob.

---

If you want to pass the clob back to the caller, and it's a temporary clob, it will have to be defined by the caller and be passed it after it's created:

create or replace procedure proc1 as
  l_clob clob;
begin
  dbms_lob.createtemporary(l_clob, true);

  proc2(l_clob);
  dbms_output.put_line('proc1 CLOB length: ' || length(l_clob));

  dbms_lob.freetemporary(l_clob);
end;
/

create or replace procedure proc2(p_clob in out clob) as
begin
  dbms_lob.open(p_clob, dbms_lob.lob_readwrite);
  dbms_lob.writeappend(p_clob, 5, '12345');
  for i in 1..9999 loop
    dbms_lob.writeappend(p_clob, 5, '.56789');
  end loop;
  dbms_output.put_line('proc2 CLOB length: ' || length(p_clob));
  dbms_lob.close(p_clob);
end;
/

exec procs;

proc2 CLOB length: 50000
proc1 CLOB length: 50000

Otherwise the object won't exist as far as the caller is concerned.

If the clob exists - selected from a table, say, so you don't need the createtemporary call - then you can just assign it to an out parameter, but I don't think that's the case for what you've described.