What Is SQL and How Does It Work

Learn how the SQL SELECT statement works, including selecting columns, filtering rows, sorting results, using aliases, expressions, DISTINCT, aggregate functions, and the practical patterns every SQL user needs to understand.

Learn how SQL joins work with simple beginner-friendly examples covering INNER JOIN, LEFT JOIN, common relationship patterns, matching rows between tables, and the mistakes new SQL users make most often.

Learn how the SQL WHERE clause works, including comparison operators, AND and OR logic, IN, BETWEEN, LIKE, NULL handling, filtering best practices, and common mistakes that cause wrong query results.

Learn how SQL window functions work, including OVER, PARTITION BY, ORDER BY, running totals, moving averages, ranking, LAG, LEAD, and the practical query patterns that make analytical SQL much more powerful.