21-Days-SQL-Challenge

At Indian Data Club, we’re on a mission to empower the next generation with practical AI and data skills. Our 21-Day SQL Challenge is designed to help beginners build a strong foundation in SQL through daily learning, hands-on practice, and real-world problem solving.

Day 1 (03/11): Introduction to SQL & SELECT Statement

Topics: Basic SELECT, column selection, viewing data structure

Day 2 (04/11): Filtering Data with WHERE Clause

Topics: WHERE clause, comparison operators, basic filtering

Day 3 (05/11): Sorting Data with ORDER BY

Topics: ORDER BY, ASC/DESC, multiple column sorting

Day 4 (06/11): LIMIT and OFFSET

Topics: LIMIT, OFFSET, pagination concepts

Day 5 (07/11): Aggregate Functions (COUNT, SUM, AVG, MIN, MAX)

Topics: COUNT, SUM, AVG, MIN, MAX functions

Day 6 (09/11): GROUP BY Clause

Topics: GROUP BY, aggregating by categories

Day 7 (10/11): HAVING Clause

Topics: HAVING clause, filtering aggregated results

Day 8 (11/11): String Functions

Topics: UPPER, LOWER, LENGTH, CONCAT, SUBSTRING

Day 9 (12/11): Date Functions

Topics: DATE functions, date arithmetic, EXTRACT

Day 10 (13/11): CASE Statements

Topics: CASE WHEN, conditional logic, derived columns

Day 11 (14/11): DISTINCT and Handling Duplicates

Topics: DISTINCT, removing duplicates, unique values

**Day 12 (15/11): NULL Handling in SQL — IS NULL, IS NOT NULL & COALESCE

Today - focus was on understanding and managing NULL values, one of the most common challenges in real datasets.

Day 13 (17/11): INNER JOIN

Topics: INNER JOIN, joining two tables, relationship understanding

**Day 14 **

🍕 The Great Pizza Analytics Challenge – SQL Mini Project

A simple SQL project to learn real-world data analysis using pizza sales data.

In this challenge, you act as a Data Analyst at The Great Pizza Company. Your job is to explore customer data, pizza information, orders, and order items to find useful business insights using SQL.

Day 15 (19/11): Multiple Joins

Topics: Joining more than two tables, complex relationships

Day 16 (21/11): Subqueries (WHERE clause)

Topics: Subqueries in WHERE, nested queries, filtering with subqueries

Day 17 (22/11): Subqueries (SELECT and FROM clause)

Topics: Subqueries in SELECT, derived tables, inline views