DBMS aka Database Management System also called a Database + Management System. The database is a group of data and Management System is a set of programs to handle the database. In short, it is defined as a technology solution to store and retrieve the data from databases. The components of DBMS like Software, Database engine, Query processor, Processors, etc. helps to facilitate the functionalities, for instance, adding, deleting, updating, retrieving the data. The DBMS also offers some amazing benefits such as Data integration, data security, data sharing, uniform management and many more.
To know more about DBMS, its pros and cons, then check our online interview questions. We have collected the best questions that will also help you to crack any interviews. Well, I want to mention that it is a hot topic in interviews, so make sure to prepare it properly. Let's start now!
Below are few major features of Dbms
Q1. What is the difference between primary key and unique key?
Difference between primary key and unique key
A primary key is a table that represents each row in the table. The primary key will not allow any duplicate value or Null value. The entered value cannot be changed in a primary key.
A unique key is also a table like a primary key, but the unique key will accept one duplicate value or Null value.
Q2. What is normalization in DBMS?
Normalization in DBMS is the term used for organizing data in the database without accepting any deletion, update or insertion. 1nf, 2nf, and 3nf are some of the examples of normalization used to organize the data in different techniques.
Q3. How many types of database languages are available in DBMS?
There are four types of database languages available in DBMS. These are as follows:
Q4. What is data abstraction in DBMS?
Database systems are composed of complex data structures and in order to be the database with user interaction, a technique was developed to hide any internal irrelevant details from Developers or users. This process of hiding from the user is known as data abstraction. There are three basic levels of this process i.e. physical, logical and view. The main purpose of this system is to provide an abstract view to the users.
Q5. Explain what is Relational Algebra?
Relational Algebra is a query language used to get input as relation and yield output of regard in a modified form. An operator can raise the query, and the most likely operator will be unary or binary. The relational queries are performed when there is a higher level of language used to handle the questions.
Q6. What is atomicity and aggregation?
In atomicity, when an ongoing transaction is incomplete, the user does not need to worry about the incompletion. DBMS ensures to complete the action. Either the operation will be completed, or the entire system will be stopped and restarted.
When a relation to be expressed within the relationships, a system is followed to execute this process. The process is termed as aggregation.
Q7. What is functional Dependency?
In DBMS, functional dependency is a relationship that exists between two attributes. It is basically a constraint that specifies the relationship between two sets of attributes where the one set can accurately determine the value of other sets and can be denoted as X → Y.
Q8. What is E-R model?
Entity-Relationship modeling represents a graphical approach for database design by utilizing the entity-relationship, it depicts real-world projects. In ER modeling, the entities are modeled along with their attributes and overall relationship among entities. Also, describe the interrelated interest in any specific domain of knowledge. The basic ER model is comprised of several and its types and specifies the relationship that exists between them.
Q9. What is Object Oriented model?
Object-oriented modeling can be defined as the construction of objects using a collection of objects that contain stored values of the instance variables found within an object. It allows for object identification and communication while supporting data abstraction, inheritance, and encapsulation.
Q10. What is BCNF?
BCNF (Boyce-Codd Normal Form) is a general form that is utilized in database normalization. It is the stronger version than the third normal form which was developed by Raymond and Edgar in 1974. It is based on the functional dependencies which take account of all the candidate keys in their precise relation and it also has the additional constants compared with the significant definition of 3NF. Its application may identify any additional redundancy which might be caused by the dependency to violate one or multiple candidate keys.
Q11. What is extension and intension?
Intension and extension, in logic, correlative words that indicate the reference of a term or concept such that intension indicates the internal content of a term or concept that constitutes its formal definition, whereas extension indicates its range of applicability by naming the particular objects that it denotes.
Q12. What is the difference between DBMS and RDBMS?
The difference between DBMS and RDBMS can be stated as DBMS applications store data as files in either a hierarchical form or a navigational form. It uses a file system to store data, so there will be no relation between the tables. Whereas RDBMS applications store data in a tabular form such that the tables have an identifier called primary key and the data values are stored in the form of tables. It is designed to handle a large amount of data.
Q13. What is a transaction?
A transaction can be defined as a single logical unit of work that accesses and possibly modifies the contents of a database. It can be also stated as any logical calculation done in a consistent model in a database is known as a transaction.
Q14. Explain the difference between attributes and identifiers.
The difference between attributes and identifiers can be stated as the attributes are properties that describe the entity's characteristics. Whereas Identifiers are attributes that name or identify entity instances.
Q15. List few the advantages of DBMS?
Some of the advantages of a Database Management System are as follows:
Q16. What is data dictionary?
A Data Dictionary is a collection of names, definitions, and attributes about data elements that are being used or captured in a database The data in a data dictionary is the metadata about the database. These elements are then used as part of a database, research project, or information system.
Q17. What is a query and sub query?
A query is an operation that retrieves data from one or more tables or views. It is a request for data or information from a database table or combination of tables. Whereas a Subquery is a type of query which is written inside another query. A subquery becomes a part of a larger query.
Q18. List few basic DDL and DML commands?
Some of the basic DDL and DML commands are as follows:
Q19. What is join? Mention its types.
JOIN is an important feature of DBMS, which is used to combine two tables based on a specified common field between them. It can be categorized in the following types:
Q20. Enlist various phases of transaction.
The various phases of transaction are as follows:
Q21. What is difference between candidate key and foreign key?
Difference between candidate key and foreign key
Candidate key - This key is a candidate for primary care for any table and it can fulfill all the requirements of the primary key which cannot be referred to as null. They have unique records for the primary key as a candidate and every table has at least one of them.
Foreign key - It is used to define the relationship between two tables. Whenever there is a need to implement a relationship between the concepts of the foreign key is used.
|Data is stored as a file.||RDBMS stores data in the form of tables.|
|It is the collection of data and the set of programs for managing the databases.||It is the database systems used for managing the relationships between the tables.|
|DBMS supports a single user only.||It supports multiple users.|
|DBMS does not support Normalization||RDBMS can be Normalized.|
|DBMS is basically for small organizations and used to handle a small amount of data.||DBMS is designed to manage a large amount of data.|
|DBMS does not support a distributed database.||RBMS offers support for distributed databases.|
|File system, XML, Windows Registry, etc. are some examples of DBMS.||Some examples of RDBMS are MySQL, Oracle, SQL Server, etc.|