A 21-day guided curriculum covering essential SQL and data manipulation concepts — from selecting columns to pivoting tables. One problem per day, progressively building your skills.

Learn SQL in 21 Days

Select and Rename Columns

Filter Rows by Condition

Find and Fill Missing Values

Sort and Top N

Group By with Multiple Aggregations

Top N Per Group

Inner Join Two Tables

Find Customers Without Orders

Join Three Tables

Percentage of Total

Conditional Column

Rank Rows Within Groups

Running Total

Rolling Average

Month-Over-Month Change

Extract and Group by Date

Days Between Events

Extract From Strings

Pivot a Table

Unpivot a Table