What would you recommend to improve the optimizer’s estimation?

View Exhibit1 to examine the description of the CUSTOMERS table.

The CUSTOMERS table has been updated heavily today. In a frequently used SQL statement,
you notice that estimated rows and the actual number of rows fetched differ greatly. The
COUNTRY_ID column has an index.
View Exhibit2 and examine the query execution plan.

What would you recommend to improve the optimizer’s estimation?

View Exhibit1 to examine the description of the CUSTOMERS table.

The CUSTOMERS table has been updated heavily today. In a frequently used SQL statement,
you notice that estimated rows and the actual number of rows fetched differ greatly. The
COUNTRY_ID column has an index.
View Exhibit2 and examine the query execution plan.

What would you recommend to improve the optimizer’s estimation?

A.
setting the STATISTICS_LEVEL parameter to ALL

B.
setting the OPTIMIZER_USE_PENDING_STATISTICS parameter to FALSE

C.
creating extended statistics for the CUST_LAST_NAME, CUST_ID, and CUST_TOTAL
columns

D.
updating the statistics for the CUSTOMERS table by using the
DBMS_STATS.GATHER_TABLE_STATS procedure



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L. Zhu

L. Zhu

if updated heavily and number of rows changed a lot, new stats required.

So D is correct