I am trying to work on a query in openerp 6.1, but it gives an error:

ProgrammingError: operator does not exist: character varying = integer LINE 1: SELECT debit,credit FROM account_move_line WHERE ref = 434 ^ HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts.

And my query:

move_obj = self.pool.get('account.move.line')
cr.execute("SELECT debit,credit FROM account_move_line WHERE  ref = %s",(move_id,))

Please help i tried looking at the typecast methods tried few but it always have some error or probably the module to be imported was missing. Its damn too urgent!