Can I select the data of the indexes?

Question

Hi everybody,
Oracle storages indexes in index type segments as I know.
Is it possible to see the data of these index segments like a table or view?
So I would like to see not only the structue of it with:
select * from dba_segments SG where SG.segment_name = ’index_name’
I think something like this:
For example if I have a table named Table1.
(please don’t see the format of the rowid):
Rowid....field1
1_1.......AA
1_2.......AB
1_3.......BB
and I have an index on field1 named ndx_t1_f1.
Create index ndx_t1_f1 on Table1(field1);
I would like to see something like this
(if it is a simple Btree index like the ndx_t1_f1):
Select * from some_schema.???ndx_t1_f1???
Rowid..........ParentRowid..........ValuePrefix..........SolutionRowid
2_1
2_11............2_1.......................A
2_12............2_1.......................B
2_111..........2_11.....................AA......................1_1
2_112..........2_11.....................AB......................1_2
2_121..........2_12.....................BB......................1_3
And if i run:
select field1 from table1 where filed1 like 'B%'
oracle can use ndx_t1_f1 index like this:
2_1 -> 2_12 -> 2_121 -> BB
Yes, I know, there are some promlems with this imagine, but is it possible, or is it a silly question?
Thanx: lados.

Answer 1

Hi,
You asked: „Why do you want to do that?”
Well, I have a table T with fields F1, F2, F3 ...
If I run:
select F2, T.* from T where F1=12345;
the result is one record and the value of F2 is ‘A’.
But if I run:
select F2, F1 from T where F1=12345;
the result is one record and the value of F2 is ‘B’.
And this is the same record. Oppps!!!!!
I think the cause of the problem is the next:
I have an index on F1, F2 named ndx_T_F1_F2
In the second case: oracle uses only the index blocks and no table blocks, because all asked data exists in the index blocks.
In the first case: oracle uses the table blocks too, because I asked all field.
And I think there is a corrupted data on the index.
I created a new index on (F1,F2,F3), and I suggest to use this.
select /*+index(T, ndx_T_F1_F2_F3)*/ T.F2 from T where F1=12345;
the result is one record and the value of F2 is ‘A’.
But what is strange, oracle didn’t realise this inconsistent situation.
(It could be an earlier crash, I don’t know, I’m new at this workplace)
I think, the problem can solve with recreating the index ndx_T_F1_F2.
But it’s a very special situation for me, and I would like to see the corrupted data concretly with my eyes.
I think, that
Select * from some_schema.???ndx_t1_f1???
would I see like a view, but it would based on procedures and not tables.
It would be enough to me, because I only could see the data in the index.
But it is impossible as you wrote, isn’t it?
Thanx: lados.