hello
  I have been using the following SQL to add a * to the beginning and the
end of accession no, and print it as barcode using barcode font.

  select '*'+alltrim(acc_no)+'*' as accessno from bookdata

and switching to delphi5/interbase, interbase seems don't like to do string
operation for me in SQL level.

select '*'+acc_no+'*' as accessno from bookdata

I don't want to do it in the front end(modify the qrdbtext or do owner
draw), just want to do it in the back end(dataset or UDF is perfered).  any
way to do it without writing UDFs?

Replace your '+' with '||'.