Top 10 DBMS Interview Questions to Prepare for in 2020

Are you preparing for a database management system interview session? If yes, then you have landed on the right page. In this blog, we will discuss the most common DBMS interview questions and answers.

Data is everywhere. It is very crucial to examine and produce meaningful outcomes from this data. There is no doubt that the demand for a database administrator is increasing day by day. The world’s most prominent organizations are looking for a database administrator.

If you are thinking of making a profession in the database sector, you should go through these DBMS interview questions and answers. If you want to know more about database management, check out our website. We provide several different technology-related courses.

DBMS Interview Questions and Answers

The below-mentioned DBMS interview questions will assist you in clearing your concepts related to database management. Here, we will discuss the top 10 questions about database management, SQL, and their answers.

Question 1: Explain DBMS. 

DBMS stands for database management systems. It is a collection of technical schemas that build and sustain a database. The database management system is software that provides a systematic method to interact with applications and databases to examine and produce the required outcome of the data. The database management system offers several operations. These include data insertion, data deletion, database creation, modification, and many more.

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Question 2: What Are the Advantages of a Database Management System?

The significant benefits of the database management system are listed below:

  • Consistency: Data is duplicated in the traditional file system. Hence, any modifications made in one part may reflect on all other parts. This further leads to inconsistent information. We need to eliminate duplicate data to remove inconsistent information throughout the system. This is possible with a DBMS.  
  • Elimination of Data Redundancy: The major reason DBMS is favored over the traditional file system is that it controls data redundancy. Each user handles their file in the conventional file systems. This further leads to redundancy of the same information in several distinct files, errors, wastage of resources, and storage space.   
  • Better Integrity: There is a lack of integrity in traditional file systems. In the DBMS approach, it is crucial to impose integrity restrictions. The database approach is much better in terms of integrity than the conventional file system because it is centralized. In the database management system, data can be utilized by several users at a time.
  • Requirements Can be Examined: With the implementation of a centralized data approach, it is much easier to analyze organizations’ needs. The primary responsibility of the database administrator is to organize a well-defined database for the organization.
  • Better Security: The traditional file system develops applications temporarily. The centralized approach of the database system provides various security constraints, which further improve the overall system’s security.

Read about: DBA Salary in India: For Freshers & Experienced

Question 3: What Is “Redo” In a Database?

“REDO” in the database is used for rollback commands. When a database transaction takes place, it goes to the database buffer cache. Then, the data is coded to “REDO” logs from the “REDO” buffer. The data recovery operations need these logs for future use. The recovery of information is not possible without these logs. The rollback command clears the undo data.

Question 4: Explain the Difference between “GROUP BY” and “ORDER BY”.

S.No. GROUP BY ORDER BY
1. The GROUP BY command is used to combined data The ORDER BY operation is used for sorting data
2. It is utilized to form summaries in the result section It is utilized for sorting results by a list of expressions

Question 5: While Creating Views, What Constraints Can You Apply?

The lists of constraints that can be applied are described below:

  • The definitions of a complete text index cannot be applied.
  • The views are only for the current database.
  • You cannot create temporary views.
  • The default definitions are not associated.
  • Integrity constraints decide the functionality of delete and insert command.
  • Triggers are associated with views.

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Question 6: Explain All Categories of Database Languages.

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The four categories of database languages are listed as below:

  • Data Manipulation Language: Data manipulation languages or DML are used to make changes in updated information. The commands for data manipulation languages include update command, select command, delete command, insert command, and many more. DML commands handle the stored information in the database. These commands are not permanent. This means rollback operation is possible in DML commands.
  • Data Definition Language: Data definition languages or DDL are used to define and update the data. The commands for data definition languages include alter, create, truncate, drop, rename, and many more. The commands of data definition languages can store shared information.
  • Transaction Control Language: Transaction control languages or TCL are used for handling database transactions. The commands for transaction control languages consist of rollback, commit, savepoint, and many more. Transaction languages are mainly used for handling the modifications made by data manipulation languages.
  • Data Control Language: Data control languages or DCL are used to take away or give database access to a user. The commands data control languages are “revoke” and “grant.” The syntax of the data control language is similar to the coding language. Data control language is related to security concerns. The GRANT DCL command provides access to the user. The REVOKE DCL command is used to withdraw the access privileges.

Question 7: What Is the Difference between Data Definition Language and Data Manipulation Language? 

S.No. Data Definition Language Data Manipulation Language
1. DDL commands are used to define the structure of the database DML commands handle the stored information in the database
2. Data definition language is not categorized further Data manipulation language is categorized as procedural DML and non-procedural DML
3. The statements of data definition language can affect the complete table The statements of data manipulation language can affect  one or more rows
4. The commands of data definition language are used to create the database structure The commands of data manipulation language are used to manipulate  the database
5. DDL commands define the table column DML commands update the table row
6. Data definition language is declarative Data manipulation language is imperative
7. DDL commands include truncate, alter, create, rename and drop, etc. DML commands include update, delete, merge and insert, etc.

Question 8: Define the Nested Loop with an Example.

It is a loop over a loop. It includes some entries of the outermost loop within an internal loop. The nested loop follows three steps. First is the identification of the outermost table. Second is allocating the internal table to the outermost table. Then, for every outermost table row, retrieve the internal table rows. Let’s consider an example.

Select row4.*, row5.* from rows, row5 where rows.row 4 =row 5.row 5;

The processing of the above query will take place in the below method:

  • For I loop (select *from row4)
  • For J loop (select * from row5 where row5=I.row 4)
  • Loop end;
  • Loop end;

Question 9: Explain the 3-Tier Database Management System Architecture.

This architecture includes a layer between the server and the client. The server-end application interacts with the client-end application for further communication process in the database system. The three-tier architecture offers GUI, which further secures the database system. The three-tier architecture consists of four levels. These levels include external, conceptual, internal, and physical levels.

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Question 10: Explain the difference between the “TRUNCATE” and the “DELETE” Command.

S.No. TRUNCATE Command DELETE Command
1. This command removes all the table rows This command deletes only specific rows of the table
2. This command doesn’t keep a log This command handles a log
3. Truncate cannot be a rollback The delete can be a rollback operation
4. Truncate is a fast command Delete is a slow command
5. The truncate command uses table log Delete command uses row log

Also Read: 15 Exciting SQL Project Ideas & Topics For Beginners

Conclusion

We hope that this article helped you discover the DBMS interview questions and answers you were looking for. These DBMS interview questions and answers will be beneficial for your interview.

We hope you will have an excellent learning opportunity in executing these projects. If you are interested to learn more about DBMS, Full-stack management and need mentorship from industry experts, check out upGrad & IIIT Banglore’s PG Diploma in Full-Stack Software Development.

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