Database & SQL Basics for SSC CGL Tier 2 Preparation

Database and SQL are among the most important topics in the Computer Awareness section of SSC CGL Tier 2. Questions from this topic test your understanding of how data is stored, organized, and managed in computer systems. Having basic knowledge of databases and SQL commands helps you answer these questions quickly and accurately.

What is a Database?

A database is an organized collection of data that can be easily accessed, managed, and updated. It stores information in a structured format, usually in tables made up of rows and columns. Databases are used in almost every sector from banking systems to government offices to store and retrieve information efficiently.

Types of Databases

Databases can be categorized based on their structure and use. Understanding the types of databases helps you know how different systems store and manage data.

Type of Database	Description
Relational Database (RDBMS)	Stores data in tables related by keys (e.g., MySQL, Oracle, SQL Server).
Hierarchical Database	Data is stored in a tree-like structure (e.g., IBM IMS).
Network Database	Data is represented using records and links (e.g., Integrated Data Store).
Object-Oriented Database	Stores data as objects, similar to programming languages (e.g., ObjectDB).
Distributed Database	Data is stored across multiple systems but acts as a single database.

Important Database Terminologies

Before learning SQL, it’s important to understand some key database terms that form the foundation of this topic.

Term	Meaning
Table	Collection of rows and columns where data is stored.
Row (Record)	A single entry or data item in a table.
Column (Field)	A specific attribute or data type in the table.
Primary Key	Unique identifier for each record in a table.
Foreign Key	Links two tables together using a common field.
Schema	The structure that defines how data is organized in a database.

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What is SQL?

SQL (Structured Query Language) is used to communicate with and manage databases. It helps in performing actions such as inserting, updating, deleting, and retrieving data from tables. SQL is easy to learn and is used in most database management systems like MySQL, Oracle, and PostgreSQL.

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Common SQL Commands

SQL commands are divided into categories based on their function. The table below lists some of the most commonly used SQL commands for SSC exams.

Command Type	Examples	Purpose
DDL (Data Definition Language)	CREATE, ALTER, DROP	Used to define and modify the structure of database objects.
DML (Data Manipulation Language)	INSERT, UPDATE, DELETE	Used to modify data within the database.
DQL (Data Query Language)	SELECT	Used to retrieve data from the database.
DCL (Data Control Language)	GRANT, REVOKE	Used to control access permissions.
TCL (Transaction Control Language)	COMMIT, ROLLBACK	Used to manage transactions in a database.

Basic SQL Queries for Practice

Here are a few simple SQL queries that help in understanding how SQL commands work. You can expect conceptual questions like these in SSC exams.

Purpose	SQL Query Example
To create a table	CREATE TABLE Students (ID INT, Name VARCHAR(50), Age INT);
To insert data	INSERT INTO Students VALUES (1, 'Rahul', 21);
To fetch all data	SELECT * FROM Students;
To update data	UPDATE Students SET Age = 22 WHERE ID = 1;
To delete data	DELETE FROM Students WHERE ID = 1;

Advantages of Using Databases

Databases make data handling more systematic and efficient. Below are some key advantages:

• Easy data storage and retrieval
• Reduces data duplication and inconsistency
• Supports multiple users simultaneously
• Provides data security and backup
• Enables data sharing and better decision-making

Key Takeaways

Below are the key takeaways:

• A database stores data in an organized manner.
• SQL is used to manage and manipulate data in databases.
• Understanding basic SQL commands like SELECT, INSERT, UPDATE, and DELETE is important for SSC CGL Tier 2.
• Relational databases are the most commonly used type.
• Regular practice of SQL-based questions improves accuracy in the Computer Awareness section.

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