Hashing | Set 1 (Introduction)

Suppose we want to design a system for storing employee records keyed using phone numbers. And we want the following queries to be performed efficiently: 
 

Insert a phone number and corresponding information.
Search a phone number and fetch the information.
Delete a phone number and related information.

Hashing Set 1 (Introduction): https://www.geeksforgeeks.org/hashing-set-1-introduction/