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Multiple Indexes - Merging
Bitmaps provide efficient merging of indexes
Assume we create another bitmap index on EMP table:
Then the query:
Will be efficiently solved via the ANDing of the two bitmap indexes
Notes:
The real power of bitmap indexes is seen as with the example in the slide when a table has multiple bitmap indexes that are referenced in a query. The two bitmaps are ANDed returning the result set very quickly.