What is database?
A database is a logically coherent collection of data with some inherent meaning, representing some aspect of real world and which is designed, built and populated with data for a specific purpose.
What is DBMS?
It is a collection of programs that enables user to create and maintain a database. In other words, it is general-purpose software that provides the users with the processes of defining, constructing and manipulating the database for various applications.
What are the advantages of DBMS?
  • Redundancy is controlled.
  • Unauthorized access is restricted.
  • Providing multiple user interfaces.
  • Enforcing integrity constraints.
  • Providing backup and recovery.
How many types of database languages are?
There are four types of database languages:
  1. Data Definition Language (DDL) e.g. CREATE, ALTER, DROP etc.
  2. Data Manipulation Language (DML) e.g. SELECT, UPDATE, INSERT etc.
  3. DATA Control Language (DCL) e.g. GRANT and REVOKE.
  4. Transaction Control Language (TCL) e.g. COMMIT and ROLLBACK.
What is DML (Data Manipulation Language)?
This language that enable user to access or manipulate data as organised by appropriate data model.
Procedural DML or Low level: DML requires a user to specify what data are needed and how to get those data.
Non-Procedural DML or High level: DML requires a user to specify what data are needed without specifying how to get those data.
What is normalization?
Normalization is a process of analyzing the given relation schemas according to their functional dependencies. It is used to minimize redundancy and also minimize insertion, deletion and update distractions.
What are the advantages of normalizing a database?
Advantages of normalizing database are as follows: 
  • Prevents duplicate entries
  • Conserves storage space
  • Improves the performance of queries
What is Denormalization?
Denormalization is the process of boosting up database performance and adding of redundant data which helps to get rid of complex data.
Describe the levels of data abstraction?
They are three levels of abstraction:
Physical level: The lowest level of abstraction describes how data are stored.
Logical level: The next higher level of abstraction, describes what data are stored in database and what relationship among those data.
View level: The highest level of abstraction describes only part of entire database.
What is RDBMS?
Relational Database Management system (RDBMS) is a database management system (DBMS) that is based on the relational model. Data from relational database can be accessed or reassembled in many different ways without having to reorganize the database tables. Data from relational database can be accessed using an API, Structured Query Language (SQL).
What is a database transaction?
Database transaction takes database from one consistent state to another. At the end of the transaction the system must be in the prior state if the transaction fails or the status of the system should reflect the successful completion if the transaction goes through.
Define the "integrity rules"?
There are two Integrity rules.
Entity Integrity: States that "Primary key cannot have NULL value"
Referential Integrity: States that "Foreign Key can be either a NULL value or should be Primary Key value of other relation.
What is Data Independence?
Data independence means that "the application is independent of the storage structure and access strategy of data". In other words, the ability to modify the schema definition in one level should not affect the schema definition in the next higher level.
Two types of Data Independence:
Physical Data Independence: Modification in physical level should not affect the logical level.
Logical Data Independence: Modification in logical level should affect the view level.
What is a view? How it is related to data independence?
A view may be thought of as a virtual table, that is, a table that does not really exist in its own right but is instead derived from one or more underlying base table. In other words, there is no stored file that direct represents the view instead a definition of view is stored in data dictionary. 
Growth and restructuring of base tables is not reflected in views. Thus the view can insulate users from the effects of restructuring and growth in the database. Hence accounts for logical data independence.
What is extension and intension?
Extension: It is the number of tuples present in a table at any instance. This is time dependent.
Intension: It is a constant value that gives the name, structure of table and the constraints laid on it.
What is Data Warehousing?
Storage and access of data from the central location in order to take some strategic decision is called Data Warehousing. Enterprise management is used for managing the information whose framework is known as Data Warehousing.
What do you mean by Index hunting?
Indexes help in improving the speed as well as the query performance of database. The procedure of boosting the collection of indexes is named as Index hunting.
How does Index hunting help in improving query performance?
Index hunting helps in improving the speed as well as the query performance of database. The followed measures are achieved to do that:
  • The query optimizer is used to coordinate the study of queries with the workload and the best use of queries suggested based on this.
  • Index, query distribution along with their performance is observed to check the effect.
  • Tuning databases to a small collection of problem queries is also recommended.
What is Data Model?
A collection of conceptual tools for describing data, data relationships data semantics and constraints.
What is Object Oriented model?
This model is based on collection of objects. An object contains values stored in instance variables with in the object. An object also contains bodies of code that operate on the object. These bodies of code are called methods. Objects that contain same types of values and the same methods are grouped together into classes.
Define B-trees.
A data structure in the form of tree which stores sorted data and searches, insertions, sequential access and deletions are allowed in logarithmic time.
Define Fragmentation.
Fragmentation can be defined as a database feature of server that promotes control on data which is stored at table level by the user.
What is Database partitioning?
Division of logical database into independent complete units for improving its management, availability and performance is called Database partitioning.
What is the importance of partitioning?
Splitting of one table which is large into smaller database entities logically is called database partitioning. Its benefits are:
  • To improve query performance in situations dramatically when mostly rows which are heavily accessed are in one partition.
  • Accessing large parts of a single partition
  • Slower and cheaper storage media can be used for data which is seldom used.
What is Atomicity and Aggregation?
Atomicity: It’s an all or none concept which enables the user to be assured of incomplete transactions to be taken care of. The actions involving incomplete transactions are left undone in DBMS.
Aggregation: The collected entities and their relationship are aggregated in this model. It is mainly used in expressing relationships within relationships.
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