RE: Column order in indices (oracle 9.2)
- From: genegurevich@xxxxxxxxxxxxxxxxxxxxx
- To: "Schultz, Charles" <sac@xxxxxxxxxxxxx>
- Date: Tue, 1 Aug 2006 08:09:17 -0500
Charles
The explain plan is pretty straightforward:
| 0 | SELECT STATEMENT | | 1 | 41 | 1 |
| | | | |
| 1 | PARTITION LIST ALL | | | | |
1 | 3 | 60,00 | PCWP | |
|* 2 | TABLE ACCESS FULL | DSPLY_ACCT_OFFR | 1 | 41 | 1 |
1 | 3 | 60,00 | P->S | QC (RAND)
And it does indicates the full table scan. When I change the SQL and add
another condition to the where clause
which filters on the leading column in the PK, the explain plan does show
the index being used. I agree that
there are other factors involved , but I don't know which ones.
thank you
Gene Gurevich
Oracle Engineering
224-405-4079
"Schultz,
Charles"
<sac@xxxxxxxxxxxx To
u> <genegurevich@xxxxxxxxxxxxxxxxxxxxx
>, "oracle-l"
08/01/2006 07:48 <oracle-l@xxxxxxxxxxxxx>
AM cc
Subject
RE: Column order in indices (oracle
9.2)
The column order does matter, but Oracle can SKIP SCAN an index in the
situation you talk about. To determine exactly what is going on, you
should at least get an explain plan of your sql. I imagine there are
other factors involved.
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of
genegurevich@xxxxxxxxxxxxxxxxxxxxx
Sent: Tuesday, August 01, 2006 7:44 AM
To: oracle-l
Subject: Column order in indices (oracle 9.2)
Hi everybody:
I remember reading that in Oracle 9.2 and higher the order of the
columns in an index does not matter.
That is oracle will be able to quickly search on a column even if it is
not a leading one. I have a table with a primary key consisting of three
columns. When a table is queried based on the third column, the data
start coming out immediately, but when I use the second column the query
just sits there.
Is that an expected behavior? Did I misunderstood something about the
column order?
thanks for any insight
Gene Gurevich
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