Basic RDBMS and SQL terms

Varanasi Software Junction July 15, 2025
Key Terms in RDBMS and SQL

📘 Key Terms in RDBMS and SQL

1. RDBMS (Relational Database Management System)

Definition: A software system that manages data using a relational model (tables, rows, columns).

Examples: MySQL, PostgreSQL, Oracle, SQL Server.

2. Table

Definition: A structured format to store data in rows and columns.

Example:

Students Table:
ID | Name  | Age
1  | Ravi  | 20
2  | Sita  | 21

3. SQL (Structured Query Language)

Definition: The language used to interact with relational databases — to create, read, update, and delete data (CRUD).

Example: SELECT * FROM Students WHERE Age > 20;

4. Primary Key

Definition: A unique identifier for each record in a table. It must be unique and not null.

Example: In the Students table, ID is the primary key.

5. Foreign Key

Definition: A field in one table that refers to the primary key in another table to create a relationship.

Example: StudentID in a Marks table referencing ID in the Students table.

6. Normalization

Definition: The process of organizing data to reduce redundancy and improve data integrity.

Forms: 1NF (Atomic columns), 2NF (Remove partial dependencies), 3NF (Remove transitive dependencies).

7. Denormalization

Definition: The process of introducing redundancy for performance optimization in queries.

Use Case: Reporting systems or analytics databases.

8. JOIN

Definition: Combines rows from two or more tables based on a related column.

Types:

  • INNER JOIN: Only matching records.
  • LEFT JOIN: All from left, matched from right.
  • RIGHT JOIN: All from right, matched from left.
  • FULL JOIN: All records from both tables.

9. Index

Definition: A database object that improves query performance by speeding up data lookup.

Example: Creating an index on `email` for fast searches.

10. View

Definition: A virtual table based on the result of a SQL query. It doesn’t store data physically.

Example: CREATE VIEW HighScores AS SELECT * FROM Scores WHERE Marks > 80;

11. Transaction

Definition: A sequence of database operations that are treated as a single logical unit of work.

ACID Properties: Atomicity, Consistency, Isolation, Durability.

12. Constraint

Definition: Rules enforced on data columns to maintain integrity.

Types: NOT NULL, UNIQUE, PRIMARY KEY, FOREIGN KEY, CHECK, DEFAULT.

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