Ascensure SQL Interview One-Shot Lecture

Introduction

• Presenter: Aman Agarwal
• Focus: SQL interview questions for Ascensure
• Prerequisite: OOPS interview one-shot video
• Importance: SQL is a crucial topic in interviews, especially for companies like Ascensure

Key Topics Covered

1. Database

• Definition: Systematic collection of electronically stored data
• Example: College database storing student data (names, roll numbers, IDs, etc.)
• Types of Data: Words, numbers, images, videos, files

2. SQL (Structured Query Language)

• Definition: Programming language for storing and processing information in a relational database
• Relational Database: Data stored in tables with rows and columns

3. DBMS (Database Management System)

• Definition: System software for creation, retrieval, updation, and management of databases
• Functionality: Allows playing with data, including creating, retrieving, updating

4. RDBMS (Relational Database Management System)

• Definition: Stores data in the form of a collection of tables
• Difference from DBMS: RDBMS specifically uses table format

5. Types of Relationships in SQL

• One-to-One: Each row in one table is linked to one row in another
• One-to-Many: One row in a table relates to multiple rows in another
• Many-to-One: Multiple rows in a table relate to one row in another
• Self-Referencing: A table is related to itself

6. SQL Queries

• Definition: Request for data or information from a database

7. Entities and Relationships

• Entities: Real-world objects (tangible or intangible)
• Relationships: Links or associations between entities

8. SQL WHERE Clause

• Functionality: Filters records to extract data fulfilling specific conditions
• Syntax: SELECT column1, column2 FROM table WHERE condition

9. SQL ORDER BY Keyword

• Purpose: Sort result set in ascending or descending order
• Syntax: ORDER BY column_name [ASC|DESC]

10. SQL Aggregate Functions

• Functions: MIN, MAX, COUNT, SUM, AVG
• Purpose: Perform calculations on multiple values

11. SQL Constraints

• Purpose: Specify rules for data in a table
• Types: Default, Unique, Not Null, Primary Key

12. SQL Index

• Purpose: Improves speed of data retrieval operations

13. SQL Joins

• Purpose: Combine rows from two or more tables
• Types:
  • Inner Join: Selects records with matching values in both tables
  • Left Join: Returns all records from the left table, matching records from the right
  • Right Join: Returns all records from the right table, matching records from the left

14. SQL Triggers

• Functionality: Execute SQL actions automatically when specific events occur

15. SQL GROUP BY Statement

• Purpose: Group result set using aggregate functions

16. SQL Support for Programming Features

• Note: SQL does not support traditional programming constructs like loops

17. SQL Aliases

• Purpose: Temporarily rename table or column names for ease
• Syntax: AS

18. NULL Value in SQL

• Definition: Indicates absence of data, differs from zero or blank space

19. Deleting Records in SQL

• Syntax: DELETE FROM table WHERE condition

Conclusion

• SQL is a critical component of technical interviews
• Further resources and mock interviews are available
• Upcoming sessions and resources for learning SQL and preparing for interviews