Blog & Tutorials
Learn SQL, one concept at a time
Clear, example-driven guides to core SQL concepts — each one pairs with the live SQL Playground so you can run every example yourself. New to SQL entirely? Start with the guide below.
How to Write SQL Queries: A Complete Beginner's Guide
Never written a line of SQL before? This is the one to read first — from what a table actually is, to writing and running your very first query, explained one small step at a time.
The SQL SELECT Statement: A Beginner's Guide
Every SQL query starts with SELECT. Learn column lists, aliases, DISTINCT, ORDER BY and LIMIT with runnable examples.
7 min read JoinsSQL JOINs Explained: INNER, LEFT, RIGHT & FULL
Visual, table-by-table walkthroughs of every join type, plus when to reach for each one.
9 min read FundamentalsThe SQL WHERE Clause: Filtering Data with Every Operator
Comparison operators, AND/OR/NOT, IN, BETWEEN, LIKE, IS NULL — and the mistakes that trip up beginners.
8 min read AggregationGROUP BY vs HAVING in SQL: What's the Difference?
The single sentence that makes this click, plus why HAVING exists when WHERE already filters rows.
6 min read IntermediateSQL Subqueries Explained: Nested SELECT Statements
Scalar, row, and correlated subqueries — where they belong in a query, and when a JOIN is the better tool.
8 min read Interview Prep25 SQL Interview Questions and Answers
From "what's the difference between WHERE and HAVING" to window functions — the questions that actually get asked.
12 min read