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SQL Boy Blog

Tutorials, guides, and insights to help you master SQL

2026-01-11
3 min read

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.

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2026-01-10
3 min read

Geospatial Analysis: Calculating Distances in 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.

sqlanalyticsgeospatialgisdata-science
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2026-01-09
3 min read

Mastering Slowly Changing Dimensions (SCD Type 2) in 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.

sqldata-engineeringetlscddata-warehouse
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2026-01-08
2 min read

Data Masking and Anonymization Techniques in SQL

Protect your users. Learn how to mask emails, hash IDs, and anonymize datasets for development and analytics environments.

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2026-01-07
3 min read

Calculating Customer Lifetime Value (CLV) in SQL

How much is a customer worth? Learn to calculate historical CLV and simple predictive CLV models using SQL.

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2026-01-06
3 min read

Sessionization: Grouping Events into User Sessions in SQL

Raw web logs are just a stream of clicks. Learn how to reconstruct meaningful "User Sessions" using SQL window functions.

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2026-01-05
3 min read

The Pareto Principle (80/20 Rule) with SQL

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.

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2026-01-04
3 min read

Market Basket Analysis in SQL: What Do Customers Buy Together?

Discover the "Beer and Diapers" correlations in your data. Learn how to use SQL self-joins to find products that are frequently purchased together.

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2026-01-03
3 min read

Dynamic SQL: Best Practices and Risks

Dynamic SQL is a double-edged sword. It offers incredible flexibility but opens the door to security nightmares. Learn how to use it safely.

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2026-01-02
3 min read

The Power of SQL LATERAL Joins (and CROSS APPLY)

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.

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2026-01-01
4 min read

Mastering ROLLUP, CUBE, and GROUPING SETS in SQL

Stop running multiple queries for subtotals. Learn how to use advanced GROUP BY extensions to generate powerful reports in a single pass.

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2025-12-31
4 min read

Solving the Gaps and Islands Problem in SQL

Master one of the most famous SQL interview questions: identifying consecutive ranges (islands) and missing sequences (gaps) in your data.

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2025-12-30
6 min read

Customer Segmentation with RFM Analysis in SQL

Learn how to implement RFM (Recency, Frequency, Monetary) analysis using SQL to segment your customers and drive targeted marketing campaigns.

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2025-12-29
3 min read

Calculating Moving Averages and Rolling Windows in SQL

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.

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2025-12-28
3 min read

Data Cleaning with SQL: From Messy to Masterpiece

Real-world data is dirty. Master 4 essential SQL functions to clean strings, handle NULLs, and fix formatting errors.

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2025-12-27
3 min read

Debugging Common SQL Logic Errors: Why Your Query is Wrong

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.

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2025-12-26
4 min read

How to Create Pivot Tables in SQL (Without the PIVOT Operator)

Learn how to transform rows into columns using standard SQL. Master the art of cross-tabulation with SUM(CASE WHEN...) for cleaner reports.

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2025-12-25
3 min read

Year-over-Year Growth Analysis in SQL

Calculate growth rates like a pro. Learn how to use the LAG() window function to compare current values with past data.

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2025-12-24
4 min read

Optimizing Large Dataset Queries: The Pagination Problem

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.

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2025-12-23
4 min read

Using Regular Expressions in SQL

Go beyond LIKE wildcard matching. Learn how to use Regular Expressions (REGEXP) in SQL to perform advanced pattern matching and data validation.

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2025-12-22
4 min read

Building Conversion Funnels in SQL

Master funnel analysis with SQL. Learn how to track user journeys from landing page to purchase and identify where you are losing customers.

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2025-12-21
4 min read

SQL Anti-Patterns: The Silent Performance Killers in Your Queries

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.

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2025-12-20
6 min read

Mastering SQL Self Joins: A Complete Guide with Interactive Examples

Stop being confused by joins on the same table. Learn how to master Self Joins for organizational hierarchies, sequential data comparison, and more.

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2025-12-19
4 min read

Descriptive Statistics in SQL: Beyond Average and Count

Take your SQL data analysis to the next level. Learn how to calculate Median, Mode, Percentiles, and Standard Deviation using modern SQL techniques.

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2025-12-18
4 min read

Mastering SQL Constraints: The Unsung Heroes of Data Integrity

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.

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2025-12-17
4 min read

SQL Data Types Deep Dive: Picking the Perfect Format for Every Column

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.

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2025-12-16
3 min read

Time Series Analysis with SQL: Trends, Growth, and Moving Averages

Turn raw timestamps into business insights. Learn how to calculate Month-over-Month growth and smooth out noisy data with 7-day moving averages.

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2025-12-15
3 min read

Working with JSON in SQL: NoSQL Powers in a Relational World

Stop choosing between SQL and NoSQL. Learn how to store, query, and filter JSON data directly within your shiny relational database.

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2025-12-14
3 min read

Mastering Recursive CTEs: The Inception of SQL

Unlock the power of WITH RECURSIVE. Learn how to traverse hierarchies, generate continuous dates, and solve graph problems directly in SQL.

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2025-12-13
4 min read

How to Read SQL Execution Plans: A Beginner’s Guide

Stop guessing why your queries are slow. Learn to read SQL execution plans, understand EXPLAIN output, and spot performance bottlenecks like full table scans.

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2025-12-12
3 min read

Understanding SQL Views: Your Virtual Tables Explained

Learn what SQL Views are, why they are useful, and how to create and use them to simplify complex queries and improve database organization.

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2025-12-11
6 min read

SQL Aggregate Functions: COUNT, SUM, AVG, MIN, MAX Explained

Master SQL aggregate functions with practical examples. Learn when and how to use COUNT, SUM, AVG, MIN, and MAX effectively.

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2025-12-10
8 min read

SQL EXISTS vs IN: When to Use Each (With Performance Tips)

Understand the difference between EXISTS and IN in SQL. Learn which performs better and avoid the NOT IN NULL trap.

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2025-12-09
8 min read

SQL ORDER BY and LIMIT: Sorting and Pagination Made Easy

Learn how to sort query results with ORDER BY and paginate data using LIMIT and OFFSET. Includes performance tips for large datasets.

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2025-12-08
6 min read

Cohort Analysis with SQL

Learn how to perform cohort analysis using SQL to track user retention, identify trends, and measure product success over time.

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2025-12-07
5 min read

Database Normalization Explained: 1NF, 2NF, 3NF

Normalization sounds scary, but it is just like organizing your messy music playlist. Learn 1NF, 2NF, and 3NF without the boring theory.

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2025-12-06
4 min read

Designing Your First Database Schema

Learn the fundamentals of database schema design, from tables and columns to relationships and normalization. Build a solid foundation for your data.

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2025-12-05
5 min read

Preventing SQL Injection: A Developer's Guide

Learn how SQL injection attacks work and how to protect your applications with parameterized queries and best practices.

securitysql-injectionbest-practicessql
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2025-12-04
5 min read

Mastering INSERT, UPDATE, and DELETE: The Complete Guide to SQL Data Manipulation

SQL is not just about reading data. Learn how to create, modify, and remove data using the core DML commands: INSERT, UPDATE, and DELETE.

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2025-12-04
4 min read

Mastering SQL Date and Time Functions

Stop struggling with dates in SQL. Learn how to handle current time, date arithmetic, formatting, and time differences using standard SQL and SQLite syntax.

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2025-12-03
4 min read

Essential SQL String Functions for Data Cleaning and Analysis

Clean, format, and extract data like a pro. Master essential SQL string functions including UPPER, LOWER, TRIM, REPLACE, SUBSTR, and concatenation.

sqlstringsfunctionsdata-cleaning
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2025-12-02
5 min read

Handling NULLs in SQL: The Ultimate Guide

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.

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2025-12-01
11 min read

Mastering SQL DISTINCT: Remove Duplicates and Find Unique Values

Master SQL DISTINCT to eliminate duplicate rows and find unique values. Learn performance tips, common pitfalls, and when to use DISTINCT effectively.

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2025-11-30
9 min read

Understanding SQL UNION: Combine Query Results Like a Pro

Learn how to use SQL UNION to combine multiple query results into a single dataset. Master UNION vs UNION ALL with practical examples.

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2025-11-29
8 min read

SQL CASE Statements: Adding Logic to Your Queries

Learn how to add conditional logic to your SQL queries using CASE statements. Transform data and categorize results with ease.

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2025-11-28
3 min read

Mastering SQL Transactions: The Art of All or Nothing

What happens when your database crashes in the middle of a payment? Learn how SQL Transactions and ACID properties keep your data safe.

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2025-11-27
4 min read

Mastering CTEs: Writing Cleaner, Better SQL

Stop writing nested subquery nightmares. Learn how to use Common Table Expressions (CTEs) to make your SQL readable, modular, and powerful.

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2025-11-27
4 min read

Understanding Database Indexes: The Key to Performance

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.

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2025-11-26
5 min read

Understanding SQL Window Functions: A Visual Guide

Master ROW_NUMBER, RANK, and running totals with interactive visualizations. See exactly how window functions process your data row by row.

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2025-11-25
7 min read

SQL Subqueries Explained: Queries Within Queries

Unlock the power of nested queries. Learn when to use subqueries in SELECT, WHERE, and FROM clauses with practical, runnable examples.

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2025-11-24
6 min read

Mastering SQL GROUP BY: From Basics to Advanced Aggregations

Learn how GROUP BY transforms rows into summaries. Watch data collapse into groups with animations and master COUNT, SUM, AVG, and HAVING.

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2025-11-23
4 min read

Mastering SQL Joins: An Interactive Guide

Stop guessing what JOINs do. Learn Inner, Left, and Cross Joins with live, interactive examples and animations running right in your browser.

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2025-11-22
3 min read

The Secret Life of a SQL Query: Order of Execution

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.

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2025-11-21
3 min read

Why Your SQL Queries Are Slow (And How to Fix Them)

Is your database crawling? Learn the 3 most common reasons for slow SQL queries and how to use the EXPLAIN command to fix them.

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2025-11-20
2 min read

Hello SQL Boy: Mastering SQL the Interactive Way

Welcome to the SQL Boy blog! Learn why we built SQL Boy and how it can help you master SQL faster than ever before.

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