
Mastering SQL Window Functions
SQL window functions explained with runnable examples: running totals, ranking with row_number, rank, and dense_rank, and period-over-period comparisons with lag and lead.
Tag

SQL window functions explained with runnable examples: running totals, ranking with row_number, rank, and dense_rank, and period-over-period comparisons with lag and lead.
Fan-out is the most dangerous bug in analytics because it makes numbers look bigger, not smaller. What grain means, how a join silently changes it, the four ways to fix double counting, and the two checks that catch it in seconds.
Stop guessing at slow SQL. A practical guide to EXPLAIN ANALYZE: how to read the plan tree, the four numbers that actually matter, why per-loop timings mislead, and why bad row estimates cause more slow queries than missing indexes.

A practical guide to breaking into analytics engineering: the T-shaped skill set to build, the portfolio that actually gets callbacks, and the mistakes that quietly sink most applications.