A database is an organized and systematic collection of data, which is stored electronically on a computer. We can add, update, delete or retrieve data from the database. A database consists of sets of tables or objects which contain records and fields. A row in the database represents a single entry and columns define the attributes which define a particular aspect or property of the table.
Problems with File System
- Data redundancy and inconsistency.
- Difficulty in accessing data
- Data isolation
- Integrity problem
- Atomicity problem
- Concurrent access anomalies
Advantages of DBMS
- Improved data sharing and integrity: Multiple users can simultaneously access the same data at any point of time.
- Reducing data inconsistency: Data inconsistency occurs when different versions of the same data occur in the database. DBMS helps to design the databases properly to reduce the data inconsistency.
- Reducing data redundancy: DBMS designs databases in such a way that duplicate data can’t be inserted in the database.
- Simple: DBMS gives a simple and logical view of the data. The operations like insertion, deletion and updation are easy to implement with the help of DBMS.
- Data abstraction: Developers use complex algorithms to increase the efficiency of the database. DBMS hides these complex algorithms and provides an abstract view of the database to the user.
- Increase end – user productivity: DBMS provides tools to convert the data into useful information, which helps the users to make quick and correct decisions.
- Increase security: DBMS provides tools like authentication and encryption to make data more reliable and secure.
As far as placements are concerned, companies need all-rounder candidates. Every software engineer should have basic knowledge of databases because no matter which technical position you are in, you may have to interact with the database. So, you will definitely require some DBMS knowledge or skills to get a placement. Studying DBMS interview questions can help you in clearing the technical rounds of the interview process.
DBMS Interview Questions – Top 20 MCQs
1. What is the full form of DDL?
- Data definition language
- Database definition language
- Database data language
- Data database language
Answer: DDL stands for Data definition language and is used to define the structure of the database.
2. Which of the following is not a command of DML?
Answer: GRANT. GRANT is a data control command and is used to provide access to the database to an user.
3. Which of the following is not a command of DDL?
Answer: SELECT. SELECT is a data manipulation command and is used to retrieve data from the database.
4. DROP command is used for?
- Deleting the entire database.
- Deleting a particular table from the database.
- Deleting all the rows of the table
- Deleting one or more rows from a table.
Answer. Deleting one or more rows from a table.
5. Which property of the DBMS is responsible to protect the data of a transaction during system failure?
Answer: Durability. The property of durability protects the data of a transaction during system failure.
6. Which normalization form is based on the transitive dependency?
- 1 NF
- 2 NF
- 3 NF
Answer: 3 BF. The 3NF is based on the transitive dependency.
7. Rows of a relation is known as?
Answer: Tuple. Rows of a relation are known as tuple.
8. What is the highest level of data abstraction?
Answer: View. View is the highest level. It simplifies the view of the database by providing multiple views of the database.
- What is the lowest level of data abstraction?
Answer: Internal. Internal level defines how the data is actually stored, it defines data-structures to store data and access methods used by the database.
10. Rectangles in ER diagram represents?
- Entry sets
Answer: Entry sets. The rectangles in the ER diagram are used to represent entity sets.
11. Which of the following allows you to uniquely identify a tuple?
- Entry sets
- Super key
Answer: Super key. Super Key helps us to uniquely identify a tuple in a relation.
12. What is the full form of NFTS?
- New Tree File System
- New Technology File System
- New Table File System
- New Transaction File System
Answer: New Technology File System.
13. Which command is used to find the number of values in a column?
Answer: COUNT. COUNT command is used to find the number of values in a column.
14. Which statement is executed automatically by the system as a side effect of the modification of the database?
Answer: Trigger. Trigger is a stored procedure in the database which is automatically executed whenever an event in the database occurs.
15. An index is clustered, if
- It is on a set of fields that form a candidate key.
- It is on a set of fields that include the primary key.
- The data records of the file are organized in the same order as the data entries of the index.
- The data records of the file are organized not in the same order as the data entries of the index.
Answer: The data records of the file are organized in the same order as the data entries of the index.
16. Primary can be ?
- NOT NULL
- Depends on the query
Answer: NOT NULL. Primary key cannot be NULL as it the key which is used to uniquely identify each row in a table.
17. Which Command is used to select some particular columns?
Answer: PROJECTION. PROJECTION is used to select some particular columns.
18. What is the Maximum children of a B- tree of order N?
- N – 1
- 2 * N
- N + 1
Answer: N. B- tree is a self balancing tree which can have a maximum of N children.
19. The number of tuples of a relation is known as?
Answer: Cardinality. Cardinality is the number of tuples of a relation.
20. Which of the following database objects does not physically exist?
- Base Index
- None of the above
Answer: View. View is just a concept and it does not exist physically.
Also you can prefer this DBMS Interview Questions article for better understanding, go and check it out!
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