SQL Revision & Practice

• Abhimanyu Saklani

A structured SQL learning repository covering SQL fundamentals, advanced SQL concepts, database design, and practical projects.

The goal of this repository is to build a strong foundation in SQL and progressively move toward advanced querying and real-world database problem solving.

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Learning Roadmap

Day	Topics	Status
Day 1	SQL Basics, DDL, DML, SELECT, Filtering, Sorting, Aggregations, GROUP BY, HAVING, Joins	Cpmpleted
Day 2	Window Functions, Views, Indexes	Completed
Day 3	CTEs, Subqueries	Completed
Day 4	Database Normalization & Database Design	Completed
Day 5	SQL Project	Upcoming

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📂 Repository Structure

SQL/
│
├── README.md
│
├── day-1/
│   ├── SQL_Basics.sql
│   └── README.md
│
├── day-2/
│   ├── Winodow_Function_Index.sql
│   └── README.md
│
├── day-3/
│   ├── SQL_CTE_Subqueries.sql
│   └── README.md
│
├── day-4/
│   ├── normalization.sql
│   └── README.md
│
└── day-5/
    ├── project.sql
    └── README.md

Each day contains:

• SQL file → Queries, examples, and practice
• README.md → Concepts, syntax, explanations, and important notes

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Day 1 — SQL Basics

Topics Covered

• Introduction to SQL

• Database fundamentals

• Tables, rows, columns

• DDL — Data Definition Language

  • CREATE
  • ALTER
  • DROP
  • TRUNCATE

• DML — Data Manipulation Language

  • INSERT
  • UPDATE
  • DELETE

• DQL

  • SELECT

• Filtering

  • WHERE
  • AND
  • OR
  • BETWEEN
  • IS NULL
  • IS NOT NULL
  • LIKE

• Sorting

  • ORDER BY

• DISTINCT

• LIMIT

• Aggregate Functions

  • COUNT()
  • SUM()
  • AVG()
  • MIN()
  • MAX()

• GROUP BY

• HAVING

• Joins

  • INNER JOIN
  • LEFT JOIN
  • RIGHT JOIN
  • FULL OUTER JOIN
  • CROSS JOIN
  • SELF JOIN

• Primary Keys

• Foreign Keys

• Constraints

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Day 2 — Advanced SQL

Topics

• Window Functions

  • ROW_NUMBER()
  • RANK()
  • DENSE_RANK()
  • LAG()
  • LEAD()
  • FIRST_VALUE()
  • LAST_VALUE()
  • PARTITION BY
  • ORDER BY inside windows

• Views

  • Creating views
  • Updating/removing views
  • Use cases

• Indexes

  • What is an index?
  • Creating indexes
  • Benefits and drawbacks
  • When to use indexes

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Day 3 — Querying Techniques

Topics

• Subqueries

  • Scalar subqueries
  • Single-row subqueries
  • Multi-row subqueries
  • Correlated subqueries
  • IN
  • EXISTS

• Common Table Expressions (CTEs)

  • WITH
  • Multiple CTEs
  • Recursive CTEs

• CTE vs Subquery

• Practical query optimization

---

Day 4 — Database Design

Topics

• Database Design

• Data Redundancy

• Data Anomalies

  • Insert anomaly
  • Update anomaly
  • Delete anomaly

• Normalization

  • 1NF — First Normal Form
  • 2NF — Second Normal Form
  • 3NF — Third Normal Form
  • BCNF

• Primary Keys

• Candidate Keys

• Composite Keys

• Foreign Keys

• Relationships

  • One-to-One
  • One-to-Many
  • Many-to-Many

• Entity Relationship concepts

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Day 5 — SQL Project

The final stage will combine the concepts learned throughout the previous days into a practical SQL project.

Project will include

• Database design
• Multiple related tables
• Primary & foreign keys
• Constraints
• Data insertion
• Data cleaning
• Joins
• Aggregate functions
• GROUP BY
• HAVING
• Subqueries
• CTEs
• Window functions
• Views
• Indexes
• Business-oriented SQL queries
• Analysis and insights

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Learning Goals

By completing this repository, I aim to be able to:

• Write SQL queries confidently
• Design relational databases
• Work with multiple related tables
• Perform data aggregation and analysis
• Write complex queries using CTEs and subqueries
• Use window functions for analytical problems
• Understand database normalization
• Understand indexes and query performance
• Solve SQL interview problems
• Apply SQL to real-world datasets and projects

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Database

The examples and practice queries in this repository primarily use:

PostgreSQL

Some syntax may differ between PostgreSQL, MySQL, SQL Server, and Oracle.

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Progress

Day 1  ████████████  SQL Fundamentals
Day 2  ████████████  Window Functions / Views / Indexes
Day 3  ████████████  CTEs / Subqueries
Day 4  ████████████  Normalization / Database Design
Day 5  ░░░░░░░░░░░░  Project

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Approach

This repository follows a learn → write → practice → apply approach.

Each topic is documented with:

1. Concept
2. Syntax
3. Example
4. Practice queries
5. Real-world use cases

The final project will bring the concepts together into one practical database and analysis workflow.

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🚀 Future Additions

Potential topics to add later:

• Transactions
• ACID Properties
• Stored Procedures
• Functions
• Triggers
• Query Optimization
• EXPLAIN / EXPLAIN ANALYZE
• Database Transactions
• Advanced PostgreSQL features
• SQL Interview Questions
• LeetCode / HackerRank SQL Practice

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Progress Tracking

• Repository setup
• Day 1 — SQL Basics
• Day 2 — Window Functions, Views & Indexes
• Day 3 — CTEs & Subqueries
• Day 4 — Normalization & Database Design
• Day 5 — SQL Project
• Final review & interview practice