Sales signals through SQL moving average
Question
Suppose you’re given the following tables, showing coat sales across a 10-day period:
Table: item_sales
| day | item_name | num_sales |
|---|---|---|
| 1 | Coat | 1055 |
| 2 | Coat | 500 |
| 3 | Coat | 300 |
| 4 | Coat | 1400 |
| 5 | Coat | 900 |
| 6 | Coat | 1000 |
| 7 | Coat | 1100 |
| 8 | Coat | 800 |
| 9 | Coat | 1350 |
| 10 | Coat | 1000 |
Using this table, write a SQL query to calculate the 3-day moving average of the number of sales, and signal when a given day is over/under that average.
Click here to view/query the tables in an interactive SQL fiddle.