You've learned that window functions exist. You've run a ROW_NUMBER() or two. But there's a whole tier of power hiding just one step further — functions that let you compare rows against their neighbors, assign competition-style rankings, and slice datasets into meaningful percentile buckets. No self-joins. No correlated subqueries. No tears. This article goes deep on five advanced window functions: LEAD , LAG , RANK , DENSE_RANK , and NTILE . Each one solves a specific class of problem you'll hit constantly in analytics, reporting, and data engineering. We'll use realistic scenarios — e-commerce orders, employee salaries, and product sales — so you can see exactly where these functions shine. Prerequisite: This article assumes you already know what the OVER() clause and PARTITION BY are. If not, check out the intro to SQL window functions first. The LEAD and LAG Functions: Looking Forward and Backward LAG retrieves a value from a previous row. LEAD retrieves a value from a future row.…