Home » Oracle » 1z0-117 » Which statement correctly describes the BITMAP AND operation?
Partial details of an execution plan.
Which statement correctly describes the BITMAP AND operation?
A. It produces a bitmap, representing dimension table rows from all dimension tables that join with qualified fact table rows.
B. It produces a concentration of the bitmaps for all dimension tables.
C. It produces a bitmap, representing fact table rows that do not join with qualified dimension table rows from all dimension tables.
D. It produces a bitmap, representing fact table rows that join with qualified dimension table rows from all dimension tables.
Correct Answer: D
Explanation/Reference:
Example:
Additional set operations will be done for the customer dimension and the product dimension. At this point in the star query processing, there are threebitmaps. Each bitmap corresponds to a separate dimension table, and each bitmap represents the set of rows of the fact table that satisfy that individual dimension’s constraints.
These three bitmaps are combined into a single bitmap using the bitmap AND operation. This final bitmap represents the set of rows in the fact table that satisfy all of the constraints on the dimension table.
Reference: OracleDatabase Data Warehousing Guide,Star Transformation with a Bitmap Index
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