Function Index with Upper

Question

I am trying to use a function index and am having trouble. I built the index successfully using the syntax:
CREATE INDEX COUNTRY_INDX1 ON COUNTRY(Upper(country_name));
Then, I submitted a query such as:
SELECT * FROM COUNTRY WHERE country_name = 'USA';
I computed EXPLAIN PLAN and it still does a FULL access of the table. If I do something like Upper(country_name) in the where clause, it still doesn't find the correct index.
Do I need to form my query differently to use the Function Index I created?
Thanks so much in advance!!!

Answer 1

SQL> desc emp
Name                                      Null?    Type
EMPNO                                              NUMBER(4)
ENAME                                              VARCHAR2(10)
JOB                                                VARCHAR2(9)
MGR                                                NUMBER(4)
HIREDATE                                           DATE
SAL                                                NUMBER(7,2)
COMM                                               NUMBER(7,2)
DEPTNO                                             NUMBER(2)
SQL> create index idx_emp_ename on emp(upper(ename)) ;
Index created.
SQL> analyze table emp compute statistics for table for all indexed columns ;
Table analyzed.
SQL> exec dbms_stats.set_table_stats(user, 'EMP', numblks => 100000) ;
PL/SQL procedure successfully completed.
SQL> set autotrace traceonly
SQL> select * from emp where upper(ename) = 'A%' ;
Execution Plan
   0      SELECT STATEMENT Optimizer=CHOOSE (Cost=60 Card=1 Bytes=40)
   1    0   TABLE ACCESS (BY INDEX ROWID) OF 'EMP' (Cost=60 Card=1 Byt
          es=40)
   2    1     INDEX (RANGE SCAN) OF 'IDX_EMP_ENAME' (NON-UNIQUE) (Cost
          =2 Card=1)
SQL>