mysql - Calculating profit of sales between dates - mysql

Question

I have a table that looks like this:
+--------+---------------------+-------+--------+-----------+
| PartNo | Date | Inv | Retail | Wholesale |
+--------+---------------------+-------+--------+-----------+
| 1 | 2018-05-12 00:00:00 | 15 | $100 | $90 |
| 2 | 2018-05-12 00:00:00 | 20 | $200 | $150 |
| 3 | 2018-05-12 00:00:00 | 25 | $300 | $200 |
| 1 | 2018-05-13 00:00:00 | 10 | $95 | $90 |
| 2 | 2018-05-14 00:00:00 | 15 | $200 | $150 |
| 3 | 2018-05-14 00:00:00 | 20 | $300 | $200 |
+--------+---------------------+-------+--------+-----------+
And I want it to look like this with a Mysql query:
+--------+------+--------+
| PartNo | Sold | Profit |
+--------+------+--------+
| 1 | 5 | $25 |
| 2 | 5 | $250 |
| 3 | 5 | $500 |
+--------+------+--------+
I need to group by PartNo while calculating the difference between totals and profits over a date range.
The unit profit has to be calculated by subtracting the wholesale from retail on the last day (or record) of the date range.
I feel like this should be easy but the differences over the date ranges are confusing me and handling records within the date range that don't start or end exactly on the date range input are losing me.
Any help would be super appreciated.
Thank you.

Answer 1

You can look up the situation at the start and at the end of the period If no start situation is found, assume no stock. If no end situation is found, that means no sales during the period.
For example for the period starting 2018-05-13 and ending 2018-05-14:
select parts.PartNo
, coalesce(FirstSale.Total, 0) - coalesce(LastSale.Total, FirstSale.Total, 0) as Sold
, (coalesce(FirstSale.Total, 0) - coalesce(LastSale.Total, FirstSale.Total, 0)) *
coalesce(LastSale.Retail - LastSale.Wholesale, 0) as Profit
from (
select PartNo
, max(case when Date < '2018-05-13' then Date end) as FirstEntry
, max(case when Date <= '2018-05-14' then Date end) as LastEntry
from Sales
group by
PartNo
) parts
left join
Sales FirstSale
on FirstSale.PartNo = parts.PartNo
and FirstSale.Date = parts.FirstEntry
left join
Sales LastSale
on LastSale.PartNo = parts.PartNo
and LastSale.Date = parts.LastEntry
Example at SQL Fiddle.

Answer 2

SELECT c.partno as partno,MAX(c.inv)-MIN(c.inv) as sold,SUM(CASE WHEN c.date = c.last_date THEN profit else 0 END)*(MAX(c.inv)-MIN(c.inv)) as profit
FROM (SELECT partno,date,inv,retail-wholesale as profit,MAX(date) OVER (partition by partno) AS last_date FROM test1)c
GROUP BY c.partno
ORDER BY c.partno;
Using the window function, first append a new column to track the max date for each partno. So the inner query inside FROM will produce rows like these with one column added to the the original dataset,
| 1 | 2018-05-12 00:00:00 | 15 | $100 | $90 | **2018-05-13 00:00:00** |
The highlighted field is the one added to the dataset which is the last date in the date range for that part number!
Now from this result, we can pull out profit by checking for the row in which date column is equal to the new column we appended, which is essentially calculating the profit for the last date by subtracting wholesale from retail and multiplying with items sold.
PS : The logic for items sold is grouping by partno and subtracting MIN(Inv) from MAX(Inv)
Link to SQL Fiddle