How to force rule to sql statement

 Dear all,

        I have a question about how to use index with the following statement?

                  SQL> select * from tableA where columnA like '%A%';

        I created index on columnA but no effect, the effect would be effect by the following query.

                  SQL> select * from tableA where columnA like 'A%';

        Hou could I improve performance from the first query?

Best regards,

Pavida