Explanation:
Index is a schema object. It is used by the oracle server to speed up the retrieval of rows by using a pointer and can reduce disk I/O by using rapid path access method to locate the data quickly. It is independent of the table it indexes. Indexes are created for column which contain a wide range of values. It can be created on the first name and last name fields of the employees table using command as

 CREATE INDEX NAME_IDX 
 ON employees(first_name, last_name); 

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