Analyzing A/B Test Results with SQL
Did the new button color actually increase sales? Learn how to calculate conversion rates, lift, and statistical significance using SQL.
Did the new button color actually increase sales? Learn how to calculate conversion rates, lift, and statistical significance using SQL.
Stop exporting to Python just to calculate distances. Learn how to perform geospatial queries like "Find locations within 5 miles" directly in standard SQL.
Data changes, but history matters. Learn how to track changes over time using the SCD Type 2 pattern to keep a perfect audit trail of your data.
Protect your users. Learn how to mask emails, hash IDs, and anonymize datasets for development and analytics environments.
How much is a customer worth? Learn to calculate historical CLV and simple predictive CLV models using SQL.
Raw web logs are just a stream of clicks. Learn how to reconstruct meaningful "User Sessions" using SQL window functions.
20% of your products likely produce 80% of your revenue. Learn how to verify the Pareto Principle in your own data using SQL window functions.
Discover the "Beer and Diapers" correlations in your data. Learn how to use SQL self-joins to find products that are frequently purchased together.
Dynamic SQL is a double-edged sword. It offers incredible flexibility but opens the door to security nightmares. Learn how to use it safely.
Discover one of the most powerful tools in modern SQL. Learn how LATERAL joins allow you to write for-each loops directly in your queries.
Stop running multiple queries for subtotals. Learn how to use advanced GROUP BY extensions to generate powerful reports in a single pass.
Master one of the most famous SQL interview questions: identifying consecutive ranges (islands) and missing sequences (gaps) in your data.
Learn how to implement RFM (Recency, Frequency, Monetary) analysis using SQL to segment your customers and drive targeted marketing campaigns.
Smooth out noisy data trends using SQL Window Functions. Learn to calculate 7-day and 30-day moving averages with AVG() OVER and ROWS BETWEEN.
Real-world data is dirty. Master 4 essential SQL functions to clean strings, handle NULLs, and fix formatting errors.
Your query runs without errors, but the numbers are wrong. Learn to spot silent killers like Fan Traps, Integer Division, and NULLs in NOT IN.
Learn how to transform rows into columns using standard SQL. Master the art of cross-tabulation with SUM(CASE WHEN...) for cleaner reports.
Calculate growth rates like a pro. Learn how to use the LAG() window function to compare current values with past data.
Why does "Page 10,000" load so slowly? Learn why OFFSET is widely considered harmful for large datasets and implementation the high-performance "Seek Method" (Keyset Pagination) in SQL.
Go beyond LIKE wildcard matching. Learn how to use Regular Expressions (REGEXP) in SQL to perform advanced pattern matching and data validation.
Master funnel analysis with SQL. Learn how to track user journeys from landing page to purchase and identify where you are losing customers.
Is your query working but slow? You might be using an Anti-Pattern. Learn about SARGability, Implicit Conversions, and why your WHERE clauses are bypassing your indexes.
Stop being confused by joins on the same table. Learn how to master Self Joins for organizational hierarchies, sequential data comparison, and more.
Take your SQL data analysis to the next level. Learn how to calculate Median, Mode, Percentiles, and Standard Deviation using modern SQL techniques.
Learn how to use SQL constraints to protect your data from "garbage in". We explore PRIMARY KEY, FOREIGN KEY, UNIQUE, and CHECK constraints with examples.
Learn how to choose the right SQL data types for performance and storage. We dive into INT vs BIGINT, VARCHAR vs TEXT, and precision management.
Turn raw timestamps into business insights. Learn how to calculate Month-over-Month growth and smooth out noisy data with 7-day moving averages.
Stop choosing between SQL and NoSQL. Learn how to store, query, and filter JSON data directly within your shiny relational database.
Unlock the power of WITH RECURSIVE. Learn how to traverse hierarchies, generate continuous dates, and solve graph problems directly in SQL.
Stop guessing why your queries are slow. Learn to read SQL execution plans, understand EXPLAIN output, and spot performance bottlenecks like full table scans.
Learn what SQL Views are, why they are useful, and how to create and use them to simplify complex queries and improve database organization.
Master SQL aggregate functions with practical examples. Learn when and how to use COUNT, SUM, AVG, MIN, and MAX effectively.
Understand the difference between EXISTS and IN in SQL. Learn which performs better and avoid the NOT IN NULL trap.
Learn how to sort query results with ORDER BY and paginate data using LIMIT and OFFSET. Includes performance tips for large datasets.
Learn how to perform cohort analysis using SQL to track user retention, identify trends, and measure product success over time.
Normalization sounds scary, but it is just like organizing your messy music playlist. Learn 1NF, 2NF, and 3NF without the boring theory.
Learn the fundamentals of database schema design, from tables and columns to relationships and normalization. Build a solid foundation for your data.
Learn how SQL injection attacks work and how to protect your applications with parameterized queries and best practices.
SQL is not just about reading data. Learn how to create, modify, and remove data using the core DML commands: INSERT, UPDATE, and DELETE.
Stop struggling with dates in SQL. Learn how to handle current time, date arithmetic, formatting, and time differences using standard SQL and SQLite syntax.
Clean, format, and extract data like a pro. Master essential SQL string functions including UPPER, LOWER, TRIM, REPLACE, SUBSTR, and concatenation.
Master the art of handling NULL values in SQL. Learn about 3-valued logic, functions like COALESCE, and how to avoid common pitfalls that break your queries.
Master SQL DISTINCT to eliminate duplicate rows and find unique values. Learn performance tips, common pitfalls, and when to use DISTINCT effectively.
Learn how to use SQL UNION to combine multiple query results into a single dataset. Master UNION vs UNION ALL with practical examples.
Learn how to add conditional logic to your SQL queries using CASE statements. Transform data and categorize results with ease.
What happens when your database crashes in the middle of a payment? Learn how SQL Transactions and ACID properties keep your data safe.
Stop writing nested subquery nightmares. Learn how to use Common Table Expressions (CTEs) to make your SQL readable, modular, and powerful.
Why is my query slow? The answer is usually indexes. Learn how database indexes work, when to create them, and how they speed up your SQL.
Master ROW_NUMBER, RANK, and running totals with interactive visualizations. See exactly how window functions process your data row by row.
Unlock the power of nested queries. Learn when to use subqueries in SELECT, WHERE, and FROM clauses with practical, runnable examples.
Learn how GROUP BY transforms rows into summaries. Watch data collapse into groups with animations and master COUNT, SUM, AVG, and HAVING.
Stop guessing what JOINs do. Learn Inner, Left, and Cross Joins with live, interactive examples and animations running right in your browser.
Ever wondered why you can't use a column alias in a WHERE clause? It's all about the order of execution. Learn how SQL actually runs your code.
Is your database crawling? Learn the 3 most common reasons for slow SQL queries and how to use the EXPLAIN command to fix them.
Welcome to the SQL Boy blog! Learn why we built SQL Boy and how it can help you master SQL faster than ever before.