UNUSED INDEX on CHAR fields

From: <sklusmann_at_my-deja.com>
Date: 2000/06/28
Message-ID: <8jcika$vir$1@nnrp1.deja.com>#1/1

I am currently trying to tune my queries and I saw with help from "EXPLAIN PLAN" that sometimes (not always) indexes on char fields are not used, e.g.:

SELECT MAX(a.v_adr + a.v_size * b.pc_size) max_size FROM varlist a, v_btypen b
WHERE a.v_typ = b.name;

OPERATION                      OPTIONS
OBJECT_NAME                    OBJECT_TYPE
------------------------------ ------------------------------

SORT
AGGREGATE NESTED
LOOPS

TABLE ACCESS                   FULL
V_BTYPEN
TABLE ACCESS                   BY INDEX ROWID
VARLIST
INDEX                          RANGE SCAN
BAUTEIL_V_TYP                  NON-UNIQUE

SELECT
STATEMENT 6 Zeilen ausgewählt

TABLE ACCESS FULL for V_BTYPEN is strange, because the field "name" of this table (char(16)) is indexed even unique and the compared field v_typ is of the same type and size.

Thanks for any explanation in advance

Stefan

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Before you buy. Received on Wed Jun 28 2000 - 00:00:00 CDT