DBMS Tutorial

Database Management System or DBMS in short refers to the technology of storing and retrieving users' data with utmost efficiency along with appropriate security measures. This tutorial explains the basics of DBMS such as its architecture, data models, data schema, data independence, E-R model, relation model, relational database design, and storage and file structure and much more.

Why Learn DBMS?

Traditionally, data was organized in file formats. DBMS was a new concept then, and all the research was done to make it overcome the deficiencies in traditional style of data management.

A modern DBMS has the following characteristics −

• Real-world entity − A modern DBMS is more realistic and uses real-world entities to design its architecture. It uses the behavior and attributes too. For example, a school database may use students as an entity and their age as an attribute.
• Relation-based tables − DBMS allows entities and relations among them to form tables. A user can understand the architecture of a database just by looking at the table names.
• Isolation of data and application − A database system is entirely different than its data. A database is an active entity, whereas data is said to be passive, on which the database works and organizes. DBMS also stores metadata, which is data about data, to ease its own process.
• Less redundancy − DBMS follows the rules of normalization, which splits a relation when any of its attributes is having redundancy in values. Normalization is a mathematically rich and scientific process that reduces data redundancy.
• Consistency − Consistency is a state where every relation in a database remains consistent. There exist methods and techniques, which can detect attempt of leaving database in inconsistent state. A DBMS can provide greater consistency as compared to earlier forms of data storing applications like file-processing systems.
• Query Language − DBMS is equipped with query language, which makes it more efficient to retrieve and manipulate data. A user can apply as many and as different filtering options as required to retrieve a set of data. Traditionally it was not possible where file-processing system was used.

DBMS Characteristics

A database is a collection of related data and data is a collection of facts and figures that can be processed to produce information. Mostly, data represents recordable facts. Data aids in producing information, which is based on facts. For example, if we have data about marks obtained by all students, we can then conclude about toppers and average marks.

A database management system stores data in such a way that it becomes easier to retrieve, manipulate, and produce information.

Following are the important characteristics of a DBMS -

• ACID Properties − DBMS follows the concepts of Atomicity, Consistency, Isolation, and Durability (normally shortened as ACID). These concepts are applied on transactions, which manipulate data in a database. ACID properties help the database stay healthy in multi-transactional environments and in case of failure.
• Multiuser and Concurrent Access − DBMS supports multi-user environment and allows them to access and manipulate data in parallel. Though there are restrictions on transactions when users attempt to handle the same data item, but users are always unaware of them.
• Multiple views − DBMS offers multiple views for different users. A user who is in the Sales department will have a different view of database than a person working in the Production department. This feature enables the users to have a concentrate view of the database according to their requirements.
• Security − Features like multiple views offer security to some extent where users are unable to access data of other users and departments. DBMS offers methods to impose constraints while entering data into the database and retrieving the same at a later stage. DBMS offers many different levels of security features, which enables multiple users to have different views with different features.

Who Should Learn DBMS?

This DBMS tutorial will especially help computer science graduates in understanding the basic-to-advanced concepts related to Database Management Systems.

Prerequisites to Learn DBMS

Before you start proceeding with this tutorial, it is recommended that you have a good understanding of basic computer concepts such as primary memory, secondary memory, and basics of data structures and algorithms.

DBMS Jobs and Opportunities

Modern technologies like big data, cloud computing, and IoT created a high demand for DBMS professionals. Almost every major company is recruiting IT professionals having good experience with DBMS.

Following are the job roles for which you can apply after learning DBMS −

• Database Administrator (DBA)
• Data Analyst
• Database manager
• Data Scientist
• Database Testers
• Cloud Database Expert
• Information Security Analyst
• Data Modeller, and many more…

So, you could be the next potential employee for any major companies who hires DBMS experts. Start learning DBMS using our simple and effective tutorial anywhere and anytime absolutely at your pace.

FAQs on DBMS

There are numerous Frequently Asked Questions (FAQs) on DBMS. Here, in this section, we have collected a set of FAQs followed by their brief answers.

1. What is a database?

A database can be defined as an organized collection of structured data or information. It can be stored either locally or on a remote server.

2. What are the components of a DBMS?

Components of a DBMS is listed below −

• Hardware − It refers to the physical machines or devices such as servers and storage systems.
• Software − It is the set of commands or programs that controls the database.
• Data − The information stored in the database.
• Data Access Language − DBMS requires a language like SQL to interact with the database.
• Users − People who interact with the database are called users. They can be database administrators, developers, and end-users.

3. What are the ACID properties in DBMS?

Atomicity, Consistency, Isolation, and Durability are known as the ACID properties of DBMS.

4. What is a database constraint?

Database constraints are some set of rules or conditions that controls behavior of a database table.

5. What is a Primary Key in a DBMS?

A primary key in DBMS is a unique identifier for a record in the specified table. It make sure that each record can be uniquely identified and cannot contain NULL values.

6. What is a Composite Key?

A composite key is a type of primary key that consists of two or more columns together to uniquely identify a record in a table.

7. What is a foreign key?

A foreign key is a column or set of columns in a table that refers to the primary key of another table, linking the two tables.

8. What is the difference between primary key and unique key?

A primary key uniquely identifies each record in a table and must not contain null values. A unique key also ensures uniqueness but can allow one null value.

• A primary key serves as the main identifier, while a unique key provides an additional constraint.
• Primary keys are indexed automatically, whereas unique keys are not indexed by default and may require manual indexing.

9. What is an ER diagram?

An ER diagram in DBMS is a visual representation of the database schema. Its full form is Entity Relationship Diagram. It shows the entities, their attributes, and the relationships among them.

10. What are entities and attributes in ER diagram?

Entities are real-world objects or concepts depicted in an ER diagram, such as students or courses. Each entity has attributes that describe its characteristics, like a student's name, age, or a course title.

Entities can be classified as strong (independent) or weak (dependent on other entities). Attributes may be simple, composite, or multivalued, each providing different levels of detail about the entity.

11. What are the different types of relationships in ER diagrams?

Different types of relationships in ER diagrams include:

• One-to-One − Each entity in one set is related to only one entity in another set.
• One-to-Many − An entity in one set can be related to multiple entities in another set.
• Many-to-Many − Multiple entities in one set can be related to multiple entities in another set.
• Recursive relationship − An entity relates to itself.

Besides these, there are identifying and non-identifying relationships that are based on dependency.

12. What is a database view?

A database view is a virtual table that is created when a query is written using data access language like SQL.

13. What is a database trigger?

A database trigger is a set of instructions that is automatically executed in response to certain events on a particular table or view.

14. What are the different types of database models?

Listed below are the different database models:

• Hierarchical model − Tree-like, parent-child relationship.
• Network model − Allows more complex record relationships.
• Relational model − It is based on tables with rows and columns. It's the most common one these days.
• Object-oriented model − Data is stored as objects, just like OOPs case in programming.
• NoSQL models − Document, key-value, wide-column, and graph databases that allow for flexible data storage.

15. What is the difference between DBMS and RDBMS?

DBMS is a broad system for managing databases. RDBMS specifically uses tables with predefined relationships.

• DBMS supports various data models, whereas RDBMS exclusively uses relational models. The data in an RDBMS is organized in structured tables, each having primary and foreign keys.
• RDBMS guarantees data integrity via normalization, allows SQL queries, and provides ACID properties. Examples include MySQL, PostgreSQL, and Oracle, which provide more robust data management than traditional DBMS.

16. Explain the three-tier architecture of DBMS.

The three-tier architecture of DBMS is a systematically organized way of managing a database. It separates functionality into three interconnected layers: presentation, application, and database.

• Presentation tier − Handles user interfaces and interaction with the system and forwards all requests to the application tier.
• Application tier − Processes these requests, implements business logic, and manages communication between the user interface and database.
• Database tier − Stores and manages actual data, maintains security and integrity, and ensures efficient data retrieval and storage.

17. What is data abstraction in DBMS and what are its levels?

Data abstraction in DBMS is a method of hiding complex data storage details from users. It consists of three levels:

• Physical Level − The lowest level that describes how data is actually stored.
• Logical Level − Describes what data is stored and the relationships between data elements.
• View Level − The highest level, showing data from individual user perspectives, with varied data representations for different user groups.

18. What is the difference between data and information?

Data refers to raw, unprocessed facts and figures lacking context, such as numbers or individual database entries. Information is data that has been organized, analyzed, and given context, revealing patterns and relationships that provide insights for decision-making.

For example, raw sales numbers are data, whereas a sales report analyzing trends and performance constitutes information.

19. What is cardinality in DBMS?

Cardinality in DBMS depicts the quantitative relationship between two different database entities. It defines the maximum and minimum number of relationships between the associated entities in an ER diagram. Common cardinality types include one-to-one, one-to-many, and many-to-many.

20. What is normalization and why is it needed?

Normalization is a technique for efficient data organization that minimizes redundancy. It involves splitting large tables into smaller, interrelated tables to eliminate data duplication.

Normalization ensures data integrity, reduces update anomalies, and enhances database performance. It is applied in normal forms like 1st Normal Form (1NF), 2nd Normal Form (2NF), and 3rd Normal Form 3NF.

21. Explain 1NF, 2NF, and 3NF with examples.

Here's a breakdown of database normal forms with examples −

22. What is BCNF (Boyce-Codd Normal Form)?

BCNF, or Boyce-Codd Normal Form, is a stricter version of 3NF that addresses multiple candidate keys.

A table is in BCNF if, for every dependency A → B, A must be a superkey. This eliminates all redundancy based on functional dependencies.

For instance, with a table containing {StudentID, Course, Professor}, where StudentID and Course together can determine Professor, we would split it into two tables to achieve BCNF: {StudentID, Course} and {Course, Professor}.

23. What is denormalization and when should it be used?

Denormalization is the process of combining multiple normalized tables into a single table, often with redundant data. This technique helps to speed up query performance by reducing the need for complex joins, which is especially useful when you need fast data retrieval. It’s commonly used in data warehouses or reporting systems, where performance is crucial and some level of data redundancy is acceptable.

However, denormalization comes with trade-offs. It can lead to increased storage requirements, and updates become more challenging since the same data might be stored in multiple places. Because of this, careful maintenance is needed to ensure that the data remains consistent and accurate.

24. What are the different types of SQL commands?

SQL commands are categorized into various types:

• DDL (Data Definition Language) CREATE, ALTER, DROP, TRUNCATE
• DML (Data Manipulation Language) INSERT, UPDATE, DELETE, MERGE
• DCL (Data Control Language) GRANT, REVOKE
• TCL (Transaction Control Language) COMMIT, ROLLBACK, SAVEPOINT
• DQL (Data Query Language) SELECT and its clauses

These commands help manage database structures, manipulate data, control access, handle transactions, and retrieve data from databases.

25. What is the difference between DDL, DML, and DCL commands?

Key differences between SQL command types:

• DDL focuses on database structure and schema, using commands like CREATE, ALTER, and DROP.
• DML handles data operations, such as adding, updating, or deleting records with INSERT, UPDATE, DELETE.
• DCL manages database access and permissions, with commands like GRANT and REVOKE.

Each command type plays a unique role in database management.

26. What is the difference between DELETE, TRUNCATE, and DROP commands?

Here's how these commands differ:

• DELETE − Removes specific records from a table based on conditions. It can be rolled back.
• TRUNCATE − Removes all records from a table at once. It cannot be rolled back. The WHERE clause cannot be used.
• DROP − Completely removes the table structure and all its data from the database. It is permanent, resulting in the loss of table definition, indexes, and constraints. It cannot be rolled back unless used within a transaction.

27. What are stored procedures?

Stored procedures basically represent precompiled SQL code blocks stored in a database. They are super useful when trying to optimize database operations and make them more secure!

28. What is database indexing?

Database indexing is one of the optimization techniques to improve various data retrieval processes. The process enables fast lookup of records in database tables through the creation of supporting data structures.

Its main objective is performance optimization: to minimize the time it takes to execute a query. It applies a balanced tree to reduce disk I/O operations. On the other hand, one should be aware of storage overhead: indexes require additional space.

29. What is the difference between clustered and non-clustered index?

Clustered indexes define the method of arrangement for physical records. Because of this, there can only be one clustered index per table. Non-clustered indexes, on the other hand, keep all their pointers separately and point to records. There can be more than one non-clustered index per table.

Clustered indexes are highly efficient while offering optimization for sequential accesses, while non clustered variations excel in queries on particular columns, though they require more space.

30. Explain COMMIT, ROLLBACK, and SAVEPOINT

These are the necessary transaction control actions:

• COMMIT − Permanently writes the transaction changes to disk, ensuring durability.
• ROLLBACK − Erases all changes since the transaction started, maintaining consistency in case of failure.
• SAVEPOINT − Sets temporary markers within a transaction to allow users to roll back to that particular point.

Together, these mechanisms provide transaction control and ensure database consistency during ongoing processing.

31. What is concurrency control?

Concurrency control mechanisms ensure controlled access to the database by simultaneous users. This protocol ensures that concurrently executed transactions do not interfere with each other, maintaining a consistent and valid state. The system aims to maximize concurrency while maintaining consistency.

32. What is hashing in DBMS?

Hashing converts search keys into direct storage addresses using mathematical functions. It enables fast data retrieval via direct addressing.

Static hashing uses fixed bucket allocations, while dynamic hashing adapts to changes in data volume. The choice of an appropriate hash function has a significant impact on performance characteristics.

33. What is query optimization?

Query optimization involves the process of selecting rapidly executable plans for database operations.

Implementation techniques are either cost-based or rule-based. Optimization significantly affects query performance by selecting a proper execution plan based on mathematical models and heuristics.

34. What are different types of joins in SQL?

Join types and their purposes include:

The selection of a join type depends on specific data retrieval requirements. Each join serves different analytical purposes while maintaining referential integrity.

35. What is referential integrity?

Referential integrity ensures that relationships between tables remain consistent using foreign key constraints. It prevents orphan records, invalid references, and inconsistent relationships.

Maintenance may require cascade operations or restricted modifications. This mechanism is fundamental for preserving database consistency.

36. What is the difference between inner join and outer join?

Inner joins strictly return matching records between tables, enforcing relationships between them. Outer joins, on the other hand, include non-matching records from one or both tables (LEFT, RIGHT, or FULL), preserving completeness for designated tables.