An index called ORD_CUSTNAME_IX has been created on the CUSTNAME column in the ORDERS table using the following command:
SQL>CREATE INDEX ord_custname_ix ON orders(custname);
The ORDERS table is frequently queried using the CUSTNAME column in the WHERE clause.
You want to check the impact on the performance of the queries if the index is not available. You do not want the index to be dropped or rebuilt to perform this test.Which is the most efficient method of performing this task?（）

Click the Exhibit button and examine the data in the EMPLOYEES and DEPARTMENTS tables.
You want to retrieve all employees, whether or not they have matching departments in the departments table. Which query would you use?（）