Analytics2026-07-21
SQL Query for Month-over-Month Growth Rate (MySQL & PostgreSQL)
Write a SQL query to calculate month-over-month growth rate using window functions. Includes LAG(), CTE approach, and handling NULL months.
SQL Guides & Tutorials
Practical SQL examples, query patterns, and tips for data analysts and developers.
Fundamentals2026-07-19
How to JOIN Three Tables in SQL: Real-World Example with Explanation
Step-by-step guide to joining 3+ tables in SQL. Covers INNER JOIN, LEFT JOIN ordering, and common mistakes that cause duplicate rows.
Window Functions2026-07-17
Calculate a Running Total in SQL: Window Function vs Self-Join
Two approaches to cumulative sums in SQL — the modern SUM() OVER() window function and the legacy self-join. With MySQL, PostgreSQL, and BigQuery examples.
Data Cleaning2026-07-14
Find and Delete Duplicate Rows in SQL (Without Deleting Originals)
How to identify duplicates with GROUP BY HAVING, and safely delete them using ROW_NUMBER() or a CTE. Works in MySQL, PostgreSQL, and SQL Server.
Guides2026-07-11
Natural Language to SQL: How AI Converts English to Database Queries
How text-to-SQL tools work under the hood — prompt engineering, schema awareness, and accuracy benchmarks. Plus when AI-generated SQL needs human review.