Databases Reference
In-Depth Information
Bitmap join index
There is also another feature: starting with Oracle 9
i
, where we can have a particular kind of
bitmap index, the bitmap join index. This is a bitmap index which represents the join between
two tables, and can be used instead of a materialized view in certain conditions.
Before creating a bitmap join index, let's see the execution plan for the following query:
CONNECT sh@TESTDB/sh
SET AUTOT TRACE EXP
SELECT SUM(AMOUNT_SOLD) AS TOTAL
FROM CUSTOMERS, SALES
WHERE CUSTOMERS.CUST_ID = SALES.CUST_ID
AND CUSTOMERS.CUST_POSTAL_CODE = '38083';
SET AUTOT OFF
In the next screenshot, we can see the execution plan needed to answer the simple question
mentioned earlier: how much have we sold for a particular customer postal code?
