DBMS Basics - Interview Questions and Answers

  1. What are the unary operations in Relational Algebra?
  2. Are the resulting relations of PRODUCT and JOIN operation the same?
    PRODUCT: Concatenation of every row in one relation with every row in another.
    JOIN: Concatenation of rows from one relation and related rows from another.
  3. What is RDBMS KERNEL?
    Two important pieces of RDBMS architecture are the kernel, which is the software, and the data dictionary, which consists of the system-level data structures used by the kernel to manage the database You might think of an RDBMS as an operating system (or set of subsystems), designed specifically for controlling data access; its primary functions are storing, retrieving, and securing data. An RDBMS maintains its own list of authorized users and their associated privileges; manages memory caches and paging; controls locking for concurrent resource usage; dispatches and schedules user requests; and manages space usage within its table-space structures.
  4. Name the sub-systems of a RDBMS.
    I/O, Security, Language Processing, Process Control, Storage Management, Logging and Recovery, Distribution Control, Transaction Control, Memory Management, Lock Management.
  5. Which part of the RDBMS takes care of the data dictionary? How?
    Data dictionary is a set of tables and database objects that is stored in a special area of the database and maintained exclusively by the kernel.
  6. What is the job of the information stored in data-dictionary?
    The information in the data dictionary validates the existence of the objects, provides access to them, and maps the actual physical storage location.