SQL> select count(*) from rdf_test where '1.0' = v1;

  COUNT(*)
----------
         1

SQL>  select count(*) from rdf_test where 'a' = v1;
 select count(*) from rdf_test where 'a' = v1
                                     *
ERROR at line 1:
ORA-01722: invalid number


SQL> select count(*) from rdf_test where v1 = 'a';
select count(*) from rdf_test where v1 = 'a'
                                         *
ERROR at line 1:
ORA-01722: invalid number