declare
   v_c pls_integer;
   v_s varchar(7) := 'params';
begin
   select 1 into v_c from table_params where lower(column_name) = lower(v_s);
   if (v_c = 1) then
      execute immediate 'update table_params set values = ''A1,A2,A3''
         where lower(column_name) = lower('''||v_s||''')';
      commit;
   end if;
end;
/