RDBMS Concepts

Question 1. What is a Database system?

Ans-The database and DBMS software together is called as Database system.

Question 2. What are the different Advantages of DBMS?

Ans- Below are the advantages of DBMS-

• Data Redundancy is controlled.
• Authentication.
• Authorization.
• Data is well integrated because of integrity constraint.
• Data backup and recovery.
• Data-dictionary(Stores data about data)

 Question 3. What is database?

Ans-A database is a organized Collection of inter-related data which can be accessed by multiple users from remote locations.

Question 4. What is DBMS?

Ans-It is a system which allows user to create and maintain a database. it is general-purpose software that provides the users with the processes of defining, constructing and manipulating the database for various their applications.

Question 5. What are the Disadvantage in File Processing System?

Ans-Below are the dis-advantages of File Processing System-

• Data redundancy
• Data inconsistency
• Problem in data access
• Data isolation
• Data integrity is not maintained
• Concurrent access issue
• Security Concerns

 Question 6. Define the “integrity rules”?

Ans-There are two Integrity rules.

• Entity Integrity: ‘Primary key cannot have NULL value’
• Referential Integrity: ‘Foreign Key can contain either a NULL value or should be Primary Key value of other relation.”

Question 7. Describe the three levels of data abstraction?

Ans-Below  are three levels of abstraction:

• Physical level: The lowest level of abstraction describes how data are stored. It is a level where data gets stored.
• Logical level: The next higher level of abstraction, describes what data are stored in database and what relationship among those data. This level hides the complexity of physical level.
• View level: This level generates user-friendly UI which ease the working for user.

Question 8. What is Data Independence?

Ans-Data independence means that ‘the application is independent of the storage structure and access strategy of data’. In simple 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: any modification in physical level should not affect the logical level.
• Logical Data Independence: any modification in logical level should affect the view level.

Question 9. What is a view? How it is related to data independence?

Ans-A view is a virtual table, a table that does not really exist but it is  derived from one or more underlying base table.
Growth and restructuring of base tables is not reflected in views.this is logical data independance.

Question 10.What is Data Model?

Ans-A collection of conceptual tools for describing data, data relationships and integrity constraints.

 Question 11.What is an Entity?

Ans-It is a ‘thing'(living or non-living) having an independent existence.

Question 12.What is E-R model?

Ans-This data model consists of basic objects called entities and  relationship among these entities.Entities are described in a database by a set of attributes.

 Question 13.What is an attribute?

Ans-It is a property of entity,which describes that entity.

Question 14.What is Weak Entity set?

Ans-An entity set whcih may not have sufficient attributes to form a primary key, and its primary key compromises of its partial key and primary key of its parent entity, then it is known as Weak Entity.

Question 15.What is DDL (Data Definition Language)?

Ans-A database schema is specifies by a set of definitions expressed by a special language called DDL.In simple words  this language handles database structure.

Question 16. What is Relationship?

Ans-It is an association among two or more entities.

Question 17.What is DML Compiler?

Ans-It translates Data manipulation statements in a query language into low-level instructions that the query evaluation engine can understand.

Question 18.What is Relational Algebra?

Ans-It is procedural query language.It consists of a set of operations that take one or two relations as input and creates a new relation.

Question 19.What is normalization?

Ans-Normalization means loss-less decomposition of data.It is a process of analysing the given relation schemas based on their Functional Dependencies and primary key

• Minimizing redundancy
• Minimizing insertion, deletion and update anomalies.

Question 20.What is Functional Dependency?

Ans-A Functional dependency is denoted by A and B. between two sets of attributes A and B that are subsets of C specifies a constraint on the possible tuple that can form a relation state C of c. The constraint is for any two tuples t5 and t6 in c if t5[A] = t6[A] then they have t5[B] = t6[B]. This means the value of A component of a tuple uniquely determines the value of component B.

Question 21.What is indexing and what are the different kinds of indexing?Ans-Indexing is a technique for determining how quickly specific data can be searched.
Below are the Types of indexing-

• Binary search style indexing
• Memory resident table
• Table indexing
• B-Tree indexing
• Inverted list indexing

Question 22.What is data dictionary?

Ans-A RDBMS maintains a description of all the data that it contains, information about every relation and index that it contains. This information is stored in a collection of relations maintained by the system called metadata. It is also called data dictionary.

 Question 23.What is meant by query optimization?

Ans-The phase that identifies an efficient execution plan for evaluating a query that has the least estimated cost is referred to as query optimization.

Question 24.What is database Trigger?

Ans-A database trigger is a PL/SQL block that can be defined to automatically execute to insert, update, and delete statements in a table. The trigger can defined to execute once for the entire statement or once for every row that is inserted, updated, or deleted. A database trigger can call database procedures that are also written in PL/SQL. There are 12 events available for which you can define a trigger.

Question 25.What are cursors give different types of cursors?

Ans- PL/SQL uses cursors for all database information accesses statements. Cursor is buffer memory which is used by a program to perform certain operation.
There are two types of cursors

•  Implicit
•  Explicit

Question 26. What is Transaction Manager?

Ans-It is a program module, which ensures that database remains in a consistent state despite system failures and concurrent transaction execution proceeds without conflicting.It ensures all the effect of transaction should be all or null.