SQL reference • for data teams • built for shipping

The modern SQL reference for analytics and product teams

Learn the clauses, functions, joins, and edge cases that shape production queries — with clear examples and a review-first mindset.

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SELECT customer_id, SUM(amount)
FROM orders
GROUP BY customer_id
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Functions

Reference pages, syntax, edge cases, and examples.

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Core SQL

The core clauses and semantics that shape every production query.

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Playground

Test SQL snippets and compare behavior in real time.

What’s inside

NULL-safe patterns and edge-case logic
Window functions and ranking semantics
Join patterns for real relational data
Production-ready SQL review checklist