A) You are implementing a Relational Database for a company t that sells its products on internet. The Database maintains the Customer information in a table called CUSTOMERS. The primary key of this table is a column called CustomerID. There are also columns LastName, FirstName , City , and ZipCode representing last name, first name, city in which the Customer lives and the 5 digit zip code of the customer respectively. When a customer calls the customer service department with any inquiries, the customer service representative asks the customer for his or her Customer ID and pulls the information related to that customer from the Database. However, if a caller does not remember his/her Customer ID, the Customer service representative asks the customer for his/her last name and the 5 digit zip code, pulls the information related to all the customers from the database with matching last name & zip code combination and then further narrows down the search for the customer record based on some other identifiable information about the customer. The CUSTOMER table is expected to have millions of records and the system needs to quickly retrieve a set of matching customer records based on Customers last name and 5 digit zip code combinations. As the Database Designer, how could you speed up the retrieval of data from the CUSTOMER table for a given combination of customers last name and zip code?

My question is that is it right to create an andex on both both last name and zip code column or create an index of each family name and code column? It must be a non clustered index? Thank you very much.

How about the other questions below?

B) You are implementing a NoSQL database to record the grievances of customers of an automobile company. You have freedom of recommending a Key-Value type database or a Document Database. Each of the grievance record is keyed on Customer ID, and contains certain other information like the Automobile model (examples: Camry, Civic, Corolla, Escort.), grievance category (Example: Mileage/Fuel consumption, Maintenance costs, pickup time), and some description of the grievance. The system needs an ability to index and query the grievance records based on values for Automobile model and grievance category. As the Database Designer, would you recommend a Key-value type of database or a Document database? Please provide explanation(s) for your recommendation.

C) You are tasked with implementing a NoSQL database for a Social Network website. The website has a requirement to identify common friends/connections between given two members. You have freedom to recommend a key-value type database, Document database or a Graph database. Which type of Database would you recommend for this type of application?