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SQL Articles & Tutorials
Expert-written tutorials, guides, and deep dives into SQL — from basics to advanced optimization. Direct answers, examples, and FAQs.
// LATEST ARTICLES41 ARTICLES
Fundamentals★ Featured
SQL Data Types Cheat Sheet: PostgreSQL, MySQL, SQL Server
A practical SQL data types reference covering numeric, string, date/time, boolean, and JSON types across PostgreSQL, MySQL, and SQL Server, with a type-selection checklist.
SqlInt team2 min read
Database Internals2 min read
SQL Indexes Explained: B-Trees, Composite, Covering
A deep dive into how SQL indexes actually work — B-tree internals, composite index column order, covering indexes, partial indexes, and the write-performance tradeoff.
SqlInt team2 min read
Interview Prep2 min read
FAANG SQL Interview Questions: A Pattern-Based Guide
Big tech SQL interviews draw from six recurring patterns, not company-specific question banks. Learn to recognize ranking, funnels, streaks, hierarchies, dedup, and schema design questions.
SqlInt team2 min read
Query Patterns2 min read
Pivot and Unpivot Data in SQL: A Practical Guide
Learn how to pivot and unpivot data in SQL using CASE, FILTER, and PIVOT/UNPIVOT operators, plus dynamic pivoting and when to reshape data in SQL vs. the application layer.
SqlInt team2 min read
Interview Prep2 min read
Top 20 SQL Interview Questions and Answers for 2026
Prepare for your SQL interview with all 20 essential questions covering joins, window functions, CTEs, indexing, transactions, and optimization, plus 5 bonus practical query challenges.
SqlInt team2 min read
Query Patterns2 min read
Nth Highest Salary in SQL: Every Method Explained
The definitive guide to finding the Nth highest salary in SQL — OFFSET/LIMIT, correlated subqueries, and DENSE_RANK, with correct tie-handling and top-N-per-group variants.
SqlInt team2 min read
Fundamentals2 min read
Date and Time Functions in SQL Compared
A side-by-side guide to SQL date and time functions across PostgreSQL, MySQL, and SQL Server — DATE_TRUNC, DATEADD, EXTRACT, and the timezone pitfalls that cause bugs.
SqlInt team2 min read
Interview Questions2 min read
Market Basket Analysis SQL Interview Explained
This is the retail and e-commerce interview classic: find product pairs frequently bought together. One line of self-join logic makes or breaks the answer.
SqlInt team2 min read
Performance2 min read
SQL Query Optimization: 10 Proven Techniques
Master SQL query optimization with 10 proven techniques, from indexing and execution plans to sargability and keyset pagination. Includes a practical optimization checklist and FAQ.
SqlInt team2 min read
Window Functions & CTEs2 min read
SQL Window Functions: The Complete Guide
A complete guide to SQL window functions — RANK, DENSE_RANK, ROW_NUMBER, LAG/LEAD, NTILE, and aggregate window functions, with frame clauses and performance notes explained.
SqlInt team2 min read
// FAQ
SQL Articles — FAQ
What SQL topics do the articles cover?
Interview prep, query patterns, window functions and CTEs, performance and optimization, fundamentals, and best practices — from beginner SELECT queries to advanced grouping, joins, and subqueries.
Are the SQL articles free?
Yes. All published articles on SqlInt are free to read with no signup required, and most include a free PDF download.
Can I download articles as PDF?
Yes. Every article page has a Download PDF button that generates a printable PDF with working links — including the free SQL cheat sheet.
How often are new articles published?
New tutorials and guides are added regularly. Subscribe via the RSS feed at sqlint.com/rss.xml to get new articles as they publish.
Where should beginners start?
Start with the Beginner and Fundamentals categories, then move to Interview Prep and Query Pattern articles once you can write basic SELECT, WHERE, GROUP BY, and JOIN queries.