Why is the query using a full table scan instead of an index scan?
A. because the histogram statistics for the COUNTRY_ID column are not updated
B. because the index statistics for the index on the COUNTRY_ID column are not current
C. because the DB_FILE_MULTIBLOCK_READ_COUNT initialization parameter is set to a higher value
D. because the optimizer predicts that most of the blocks in the table are accessed. Therefore, it uses a full table scan, even though indexes are available.
Answer:D
Why is the query using a full table scan instead of an index scan?
A. because the histogram statistics for the COUNTRY_ID column are not updated B. because the index statistics for the index on the COUNTRY_ID column are not current C. because the DB_FILE_MULTIBLOCK_READ_COUNT initialization parameter is set to a higher value D. because the optimizer predicts that most of the blocks in the table are accessed. Therefore, it uses a full table scan, even though indexes are available.