Blob to clob conversion when inserting as select?

Question

I have a table with one row that has BLOB column. I would like to copy that row to a different table, with CLOB column data type. I’ve found this discussion (BLOB to CLOB? where some examples of stored procedures to convert blob to clob are used but I am unsure what should I use as input parameter to the blob_to_clob procedures listed in that discussion? Please advice.
Thank you very much for your time.
Daniel

Answer 1

The function by Richard Wiener {message:id=9646697} in the thread simply uses the procedure dbms_lob.converttoclob with a set of parameters defined in the function.
At my work we have created a similar function:
CREATE OR REPLACE function blob2clob (p_blob in blob)
   return clob
is
   v_clob     clob;
   amount         INTEGER;
   dest_offset    INTEGER;
   src_offset     INTEGER;
   blob_csid      NUMBER;
   lang_context   INTEGER;
   warning        INTEGER;
begin
   dbms_lob.createtemporary (
      v_clob,
      false,
      dbms_lob.session
   amount         := dbms_lob.lobmaxsize;
   dest_offset    := 1;
   src_offset     := 1;
   blob_csid      := nls_charset_id('AL32UTF8');
   lang_context   := 0;
   dbms_lob.converttoclob(
      v_clob,
      p_blob,
      amount,
      dest_offset,
      src_offset,
      blob_csid,
      lang_context,
      warning
   return v_clob;
end blob2clob;
/Difference here is that Richard uses default charset - we have need for AL32UTF8 charset. You should use whatever is relevant for your case.
The use of either Richards function or the above is simple for your insert as select:
insert into tab_c (clob_col)
select blob_to_clob(blob_col) from tab_b