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SQL Fundamentals — Query Any Database

The one language every developer needs. Learn SQL from simple selects to complex joins, subqueries, and aggregations. Practical patterns for real-world data questions. Works with PostgreSQL, MySQL, SQLite, SQL Server — core SQL is universal. Stop guessing at queries. Understand what you're asking the database to do.

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8
Lessons
387
Questions

Sample Flashcards from This Course

Here's a preview of what you'll learn:

Q1: Match each ON DELETE action with what happens when a referenced row is deleted:
Q2: 🎯 In a well-formatted SQL query, clauses like SELECT, FROM, WHERE, and ORDER BY should be {{1}}, and complex logic should include {{2}} explaining the intent.
Q3: 📥 The {{1}} operator tests if a value exists in a subquery's result set, while the {{2}} operator tests whether a subquery returns any rows at all.
Q4: 📊 Fill in the blank: The _______ clause is required after every window function to define the window specification.
Q5: 🔧 Fill in the blank: The solution to the N+1 query problem is to use a ___ to fetch all related data in a single query.

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