SQL server find previous sales based on previous draw for the same day

Question

I have below dataset

I'm looking for an SQL server query to get below output that will calculate previous sales based on previous draw number for the same day

Answer 1

You can use LAG to do this.

SELECT RETAILER_NUMBER, DRAW_NUM, DAY_NAME, ACTUAL_SALES,
       LAG(ACTUAL_SALES, 1, 0) OVER (PARTITION BY RETAILER_NUMBER, DAY_NAME ORDER BY DRAW_NUM) AS PREVIOUS_SALES
FROM YOUR_TABLE