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Show How To Compute Existence Bitmaps From Other Bitmaps. Make Sure That Your Technique Works Even In The Presence Of Null Values, By Using A Bitmap For The Value Null?

Answer»

The existence BITMAP for a relation can be calculated by taking the union (logical-or) of all the BITMAPS on that attribute, INCLUDING the bitmap for value NULL.

The existence bitmap for a relation can be calculated by taking the union (logical-or) of all the bitmaps on that attribute, including the bitmap for value null.



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