Case insensitive search and index

Question

I have to execute a case insentitive search.
I created this index on a not null field:
create index indx_prova on
table (nlssort(campo, 'NLS_SORT=BINARY_CI'));
The select is:
select * from tabella where campo like 'A storage%'
This select should retrive 5 records:
A storage ring for crystalline beam studies
a storage ring for crystalline beam studies
A Storage Ring for Crystalline Beam Studies
A storage ring for crystalline beam studies
A storage ring for crystalline beam studies
Instead I got only 3 records:
A storage ring for crystalline beam studies
A storage ring for crystalline beam studies
A storage ring for crystalline beam studies
So The query isn't case insensitive.
I can't set nls_sort=BINARY_CI and nls_comp=LINGUISTIC at level session.
Is there a solution.
Am I doing something wrog?

Answer 1

I set alter session set nls_comp=LINGUISTIC; alter session set nls_sort=BINARY_CI;
I create this index:
create index titolo_indx on
table (nlssort(campo, 'NLS_SORT=BINARY_CI'));
If I execute this query:
select * from ri01_prodotti where titolo like 'A storage ring f%'
Oracle doesn't user the index.
SQL_ID 7yvspnyf96vp8, child number 0
select * from ri01_prodotti where titolo like 'A storage ring%'
Plan hash value: 350479533
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | | | 2020 (100)| |
|* 1 | TABLE ACCESS FULL| TABLE | 1 | 1365 | 2020 (1)| 00:00:25 |
Predicate Information (identified by operation id):
1 - filter("CAMPO" LIKE 'A storage ring%')
If I execute a query with =, oracle use index.
select * from table where campo ='A storage ring for crystalline beam studies'
SQL_ID 5jzr5nm6b37pq, child number 0
select * from ri01_prodotti where titolo ='A storage ring for crystalline beam
studies'
Plan hash value: 3866031381
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | | | 151 (100)| |
| 1 | TABLE ACCESS BY INDEX ROWID| RI01_PRODOTTI | 377 | 502K| 151 (0)| 00:00:02 |
|* 2 | INDEX RANGE SCAN | TITOLO_INDX | 151 | | 3 (0)| 00:00:01 |
Predicate Information (identified by operation id):
2 - access("RI01_PRODOTTI"."SYS_NC00078$"=HEXTORAW('612073746F726167652072696E6720
666F72206372797374616C6C696E65206265616D207374756469657300') )