View Exhibit1 and examine the indexes on the CUSTOMERS table.The statistics for the CUSTOMERS table have been updated recently by using the following command:SQL> EXEC -DBMS_STATS.GATHER_TABLE_STATS('SH','CUSTOMERS',method_opt=>'FOR ALLINDEXED COLUMNS SIZE AUTO');View Exhibit2 to examine a query plan. Even though the index is present on theCOUNTRY_ID and CUST_GENDER columns, the query uses a full table scan. What could be the reason?
View Exhibit1 A 1 (124.47 KiB) Viewed 141 times
View Exhibit1 A 2 (124.47 KiB) Viewed 141 times
A. because the histogram statistics for the COUNTRY_ID column are not updated
B. because the DB_FILE_MULTIBLOCK_READ_COUNT initialization parameter is set to a high value
C. because the optimizer calculates the cost of accessing blocks by using a full table scan to be less as compared to index scans, even though indexes are available
D. because indexes on CUST_GENDER and COUNTRY_ID columns are of different types, the index on the CUST_GENDER column is bitmap index, and on COUNTRY_ID columns is btree index.
Join a community of subject matter experts. Register for FREE to view solutions, replies, and use search function. Request answer by replying!