index part of column with flexible number of character - oracle

Question

I want to index part of a column with value like this : #aaa/453 . it means that the value in this column consist of four parts , symbol character / number .
in our query we just have Numerical section so we want to have an index on this part.
the number of character in each part is changeable .
please help me

Answer 1

Here's an example: table contains values similar to what you described.
SQL> create table test (col varchar2(20));
Table created.
SQL> insert into test
2 select '#aaa/453' from dual union all
3 select '$bcdxyz/35' from dual union all
4 select '#gf/203' from dual;
3 rows created.
In order to select rows from the table, one option is to use such a query:
SQL> select * from test
2 where regexp_substr(col, '\d+$') = '35';
COL
--------------------
$bcdxyz/35
So, let's create a function-based index:
SQL> create index i1test on test (regexp_substr(col, '\d+$'));
Index created.
What does the explain plan say?
SQL> explain plan for
2 select * from test
3 where regexp_substr(col, '\d+$') = '35';
Explained.
SQL> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------
Plan hash value: 210954056
--------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 54 | 2 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| TEST | 1 | 54 | 2 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN | I1TEST | 1 | | 1 (0)| 00:00:01 |
--------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access( REGEXP_SUBSTR ("COL",'\d+$')='35')
Note
-----
- dynamic sampling used for this statement (level=2)
18 rows selected.
SQL>
Looks like it might help. Try it, see how it behaves.