Aggregation

  1. GROUP BY & Aggregates β€” Compute counts and sums; HAVING for post-aggregate filters.
  2. 🚧 HAVING vs WHERE β€” Pre-aggregate vs post-aggregate filtering.
  3. 🚧 Window Basics β€” ROW_NUMBER, RANK, DENSE_RANK.
  4. 🚧 Window Aggregates β€” SUM() OVER, running totals, moving averages.
  5. 🚧 Window Frames β€” ROWS vs RANGE, peers, gaps & islands.
  6. 🚧 Grouping Sets β€” ROLLUP, CUBE, and GROUPING SETS.