window-functions

Window functions perform calculations across row sets without grouping. ROWNUMBER assigns unique sequential numbers. RANK/DENSERANK handle ties differently. I use PARTITION BY to reset calculations per group. ORDER BY determines calculation order with

A surprising amount of feature engineering is best done in SQL before Python ever runs. ROW_NUMBER, LAG, rolling windows, and partitioned aggregates are ideal for deriving customer behavior signals close to the source. I use SQL here when it reduces m