The columns CUST_CITY, CUST_STATE_PROVINCE, and COUNTRY_ID are frequently used together in the WHERE clause of the queries. The CUSTOMERS table is a big table with 20 GB of data. You notice that the selectivity for these three columns varies from the selectivity that the optimizer calculates.
What would you recommend to influence the selectivity calculated by the optimizer?
A.
creating function-based indexes by concatenating all the columns
B.
updating histogram statistics for these columns by using the DBMS_STATS.GATHER_TABLE_STATS procedure
C.
using the DBMS_STATS.CREATE_EXTENDED_STATS function to create a virtual column and create index on the virtual column
D.
using the DBMS_STATS.CREATE_EXTENDED_STATS function to create a virtual column and the DBMS_STATS.GATHER_TABLE_STATS procedure to collect statistics on the virtual column