SQL & PL/SQL

Hi All,

We have a query like below

Select Columns
from T1,t2,t3
where t1.c = t2.c2
and t1.c = t3.c3
and t1.Col in 
SELECT :Col
  FROM xmltable('r/c' passing
                xmltype('<r><c>' ||
                        replace(REPLACE(:Col1 || ', ' ||
                                        DECODE(:Col_2_Decode,
                                               '1',
                                               :Col_1,
                                               '2',
                                               :Col_1,
                                               '') || ',' ||
                                        DECODE(:Col_2_Decode, '2', :Col2, ''),
                                        ''''),
                                ',',
                                '</c><c>') || '</c></r>') columns new_str
                varchar2(50) path '.') d

How else we can rewrite this, this seems to be a bit clumsy and also performance wise not ok. I am not in a position to share the exact query with sample data, sorry for the same.  Hence I would like to hear from the Pro's on how better or best to have this rewritten by some other way or function built-ins available in 11g. Thanks in advance.