Oracle Cumulative Calculation using Windows Analytical functions - sql

Question

I am new to Windows functions (lag, lead etc) and I am using Oracle. I did some research and tried few solutions but I couldnt get the desired result.
I have an inventory table, where I want to find out the items used and the remaining item left on the given day.
The data comes in as follows
Dates | Items | Total_Inv_Items | Damaged_Items | Sellable_Items | Sold_Items | Remaining_Items
11/13/2020 Pen 999 15 984 109 875
11/13/2020 Book 401 6 386 109 277
11/14/2020 Pen 0 0 0 121 0
11/14/2020 Book 0 0 0 121 0
11/15/2020 Pen 0 0 0 31 0
11/15/2020 Book 0 0 0 31 0
11/16/2020 Pen 201 3 198 33 165
11/16/2020 Book 301 5 296 33 263
Useable_Items and Remaing_Items are caluclated columns.
Sellable_Items = Total_Inv_Items - Damaged_Items
Remaning_Items = Sellable_Items - Sold_Items
Total_Inv_Items is manufacture or new items available in the store.
The desired output:
Dates | Items | Total_Inv_Items | Damaged_Items | Sellable_Items | Sold_Items | Remaining_Items
11/13/2020 Pen 999 15 984 109 875
11/13/2020 Book 401 6 386 109 277
11/14/2020 Pen 0 0 875 121 754
11/14/2020 Book 0 0 277 121 156
11/15/2020 Pen 0 0 754 31 721
11/15/2020 Book 0 0 156 31 125
11/16/2020 Pen 201 3 919 33 886
11/16/2020 Book 301 5 421 33 388
The remanining item is cummulative and the sellable items changes whenever there is a new item added to the inventory or it is same as previous days remaining item.
Query that gives me first data
SELECT
Date,
Items,
NVL(Total_Inv_Items, 0) as Total_Inv_Items,
NVL(Round(Total_Inv_Items * DamagePercentage/100), 0) as Damaged_Item,
Round(Total_Inv_Items - (Total_Inv_Items * DamagePercentage/100)) as Sellable_Items,
Sold_Items,
Round(Total_Inv_Items - (Total_Inv_Items * DamagePercentage/100))- Sold_Items as Remaining_Items
FROM
Table
Order By
Date
Note:
If you notice on Nov 16th there was new items that was available in the store so it adds to the previous days remaining items(Ex Pen 201-3+721).

Answer 1

You can use the lag function as follows:
SELECT Date,
Items,
Total_Inv_Items,
Damaged_Item,
-- FOLLOWING IS CALCULATED EXPRESSION BASED ON YOUR FORMULA: Pen 201-3+721
Total_Inv_Items
- Damaged_Item
+ COALESCE(LAG(Remaining_Items) OVER (PARTITION BY ITEMS ORDER BY DATE),0) AS Sellable_Items,
-- EXPRESSION ENDS HERE
Sold_Items,
Remaining_Items
FROM
(SELECT DISTINCT
Date,
Items,
NVL(Total_Inv_Items, 0) as Total_Inv_Items,
NVL(Round(Total_Inv_Items * DamagePercentage/100), 0) as Damaged_Item,
Round(Total_Inv_Items - (Total_Inv_Items * DamagePercentage/100)) as Sellable_Items,
Sold_Items,
Round(Total_Inv_Items - (Total_Inv_Items * DamagePercentage/100))- Sold_Items as Remaining_Items
FROM Table)
Order By Date
This expression should be placed in the outer query. The inner query should be your query which is giving the first data.

Answer 2

I think you just want cumulative sums and arithmetic:
select t.*,
sum(total_inv_items - damaged_items) over (partition by item order by date) as sellable_items,
sum(total_inv_items - damaged_items - sold_items) over (partition by item order by date) as remaining_items
from t
order by date;

Answer 3

Thanks #Gordon Linoff and #Tejash, your comments helped me to resolve this issue. The following code gave me the desired result.
NOTE: 1.5 is the pecentage of Damaged Items which I have included it directly in the query, most of the time its comes from the DB.
SELECT
Dates,Items,
Total_Inv_Items,
Damaged_Item,
CASE
WHEN Total_Inv_Items = 0 THEN LAG(Remaining_Items) OVER (partition by items order by dates)
ELSE Sellable_Items+NVL(LAG(Remaining_Items) OVER (partition by items order by dates),0)
END as Sellable_Items,
Sold_Items,
Remaining_Items
FROM
(
SELECT
Dates,Items,
Total_Inv_Items,
Damaged_Item,
Sellable_Items,
Sold_Items,
SUM(Sellable_Items - Sold_Items) OVER (partition by items order by dates) as Remaining_Items
FROM
(
SELECT
Dates,
Items,
NVL(Total_Inv_Items, 0) as Total_Inv_Items,
NVL(Round(Total_Inv_Items * 1.5/100), 0) as Damaged_Item,
Round(Total_Inv_Items - (Total_Inv_Items * 1.5/100)) as Sellable_Items,
Sold_Items,
Round(Total_Inv_Items - (Total_Inv_Items * 1.5/100))- Sold_Items as Remaining_Items
FROM
Table T
) A
)B
Order By
Dates