Days of supply: formula and example.

WITH demand AS (
  SELECT product_id, SUM(ABS(quantity)) / 30.0 AS avg_daily_demand
  FROM stock_movements
  WHERE movement_type = 'sale'
    AND movement_date >= current_date - interval '30 days'
  GROUP BY product_id
),
on_hand AS (
  SELECT product_id, SUM(quantity) AS qty
  FROM stock_levels
  WHERE snapshot_date = (SELECT MAX(snapshot_date) FROM stock_levels)
  GROUP BY product_id
)
SELECT p.sku, p.name, oh.qty AS on_hand,
       ROUND(d.avg_daily_demand, 1) AS avg_daily_demand,
       ROUND(oh.qty / NULLIF(d.avg_daily_demand, 0), 1) AS days_of_supply
FROM on_hand oh
JOIN products p ON p.product_id = oh.product_id
LEFT JOIN demand d ON d.product_id = oh.product_id
ORDER BY days_of_supply NULLS LAST;

Avg Daily Demand = DIVIDE(CALCULATE(SUMX(StockMovements, ABS(StockMovements[Quantity])), StockMovements[MovementType] = "sale", DATESINPERIOD('Date'[Date], MAX('Date'[Date]), -30, DAY)), 30)
Days of Supply = DIVIDE(CALCULATE(SUM(Stock[Quantity]), LASTNONBLANK('Date'[Date], CALCULATE(SUM(Stock[Quantity])))), [Avg Daily Demand])