In this video, I break down how to master SQL in 2026 using five very real levels—because “SELECT, JOIN” is cute, but that’s only Level 1. Level 1 is where you can write basic queries (select/where/join/group by) to pull data, count users, and sum revenue. Useful, but you’re mostly following instructions. Level 2 is where you analyze with SQL using window functions, CTEs, subqueries, date trunc, and case when—now you’re building logic, calculating rolling averages, ranking users, and doing month-over-month comparisons to answer actual business questions. Level 3 is where you understand what breaks things: null handling, unions, execution order (SQL doesn’t run top to bottom), and why left joins can duplicate rows. This is the level where people start trusting your dashboards. But the level most people skip—and you shouldn’t—is Level 4: scaling and efficiency. Indexes, partitions, EXPLAIN, and performance tuning help you understand why a query takes 30 seconds vs 2 seconds, reduce scan size, and work efficiently with massive tables (think 500 million rows). Finally, Level 5 is where you think with SQL: funnels, cohorts, retention curves, experiment metrics, and definitions—so you’re not just answering requests, you’re shaping decisions.