DBMS - Interview Questions and Answers

  1. What is the difference between a Java servlet and a Java applet?
    An applet is a compiled Java bytecode program that is transmitted to a browser via HTTP and is invoked using the HTTP protocol on the user's workstation. A servlet is a Java program that is invoked on the server to respond to HTTP requests.
  2. What is the coding pattern for using a JDBC driver?

    1. Load the driver.

    2. Establish a connection to the database.

    3. Create a statement.

    4. Do something with the statement.

  3. What is a Java bean?
    A Java bean is a Java class that has the following three properties. (1) There are no public instance variables. (2) All persistent values are accessed using methods named getxxx and setxxx. (3) The bean class must either have no constructors or it must have one explicitly defined zero-argument constructor.
  4. How are surrogate keys and metadata handled in MySQL?
    MySQL uses integer data types combined with the property AUTO_INCREMENT to create surrogate keys. This creates a sequence that starts at one (1) and increases by one (1) for each new record. MySql maintain its metadata in a database named mysql. For example, this database maintains two tables named user and db.
  5. What is a data mart?
    A data mart is a collection of data smaller in scope and size than a data warehouse. It is dedicated to data from a particular business component of business functional area. A data mart may function as a subset of a larger data warehouse. Users of a data mart are usually knowledgeable analysts in the business area using the data mart.
  6. What is RFM analysis?
    RFM analysis is a Business Intelligence (BI) reporting system that analyzes and ranks customers based on their purchasing patterns. R refers to "how recently" a customer placed an order, F refers to "how frequently" the customer orders, and M refers to "how much money" the customer spends. Typically, the customers are ranked into "20%" groups and assigned a number to represent their ranking. Thus 1 means top 20%, 2 the next 20% and so on. In this system a score of 1 is best and a score of 5 is worst. Thus a customer with an RFM score = 1 5 1 would be one who has ordered recently, does not order frequently, and who makes large purchases.

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