Cognizant Exam Preparation Overview

Introduction

• Preparing for Cognizant exam
• Focus on communication and technical rounds
• Emphasis on repeated patterns from previous years
• Importance of taking notes and marking answers

Topics Covered

• SQL (Structured Query Language)
  • SQL commands: DDL, DML, DCL, TCL
  • Understanding constraints and their types
• Other topics:
  • Unix commands
  • Shell scripting
  • Data warehousing basics
  • ETL (Extract, Transform, Load)
  • Cloud fundamentals

SQL Questions and Answers

1. Create Table

   • Query: CREATE TABLE students (ID INT PRIMARY KEY, name VARCHAR(255));
   • Difference between VARCHAR and CHAR
     • VARCHAR allocates space based on the length of the input, while CHAR allocates fixed space.

2. Insert Data

   • Query: INSERT INTO students (ID, name) VALUES (1, 'Alex');

3. Update Data

   • Query: UPDATE students SET name = 'Alice' WHERE ID = 1;

4. Delete Data

   • Query: DELETE FROM students WHERE ID = 1;

5. Select with Condition

   • Query: SELECT * FROM students WHERE ID > 5;

6. Count Total Students

   • Query: SELECT COUNT(*) FROM students;

7. Joining Tables

   • Query: SELECT s.name, g.grade FROM students s JOIN grades g ON s.ID = g.student_id;

8. Subquery

   • Query to find the name of the student with the highest ID:
     • SELECT name FROM students WHERE ID = (SELECT MAX(ID) FROM students);

9. Create View

   • Query: CREATE VIEW student_view AS SELECT * FROM students WHERE ID > 5;*

Unix Commands Overview

• Basic Commands:

  • ls: List files and directories
  • cd: Change directory
  • rm: Remove files
  • pwd: Print working directory
  • touch: Create a new file

• Special Symbols:

  • ~: Represents the current user's home directory

• Shell Scripting:

  • Use # for comments in scripts

Data Warehousing Concepts

• ETL Process:
  • Extract, Transform, Load
• Types of Data Warehouses:
  • Enterprise Data Warehouse, Operational Data Store, Data Mart
• Key Purpose of Data Mart:
  • Store specific subset of data for business units

Cloud Computing Basics

• Advantages of Cloud Computing:
  • Scalability of resources
  • Cost-effective pay-as-you-go model
• Platforms:
  • PaaS (Platform as a Service) for building applications

Conclusion

• Recommended to practice SQL questions and Unix commands
• Encourage joining communities for support
• Emphasize on continuous preparation and feedback

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• Comment with homework and questions for further assistance.