SQL Group by and update/delete row - sql

Question

I have a SQL.Table
CREATE TABLE [dbo].[Stack_Example](
[ID] [bigint] NOT NULL,
[Product_ID] [bigint] NULL,
[Quantity] [decimal](18, 2) NULL,
[Price] [decimal](18, 2) NULL,
CONSTRAINT [PK_Stack_Example] PRIMARY KEY CLUSTERED
(
[ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
With data like shown under:
INSERT [dbo].[Stack_Example] ([ID], [Product_ID], [Quantity], [Price]) VALUES (1, 25, CAST(55.00 AS Decimal(18, 2)), CAST(1000.00 AS Decimal(18, 2)))
GO
INSERT [dbo].[Stack_Example] ([ID], [Product_ID], [Quantity], [Price]) VALUES (2, 25, CAST(1.00 AS Decimal(18, 2)), CAST(1000.00 AS Decimal(18, 2)))
GO
INSERT [dbo].[Stack_Example] ([ID], [Product_ID], [Quantity], [Price]) VALUES (3, 26, CAST(1.00 AS Decimal(18, 2)), CAST(500.00 AS Decimal(18, 2)))
GO
So my problem here is i need to group those items by Price, Product_Id and SUM(Quantity).
There is need for Update/Delete query assuming my output window need to looks like
Its simple when you do a select query
select Product_ID,SUM(Quantity) AS Quantity,Price from Stack_Example
Group by Product_ID,Price
So at very begin what i need to do is to delete the row with id : 2 And update the row with id 1 set Quantity = Quantity + 1 ( Quantity of deleted row ).
So when i run the select query without grouping and summing i need to get the same output
UPDATE Stack_Example SET Quantity = (SELECT SUM(Quantity)
FROM Stack_Example child
WHERE child.Product_ID = Stack_Example.Product_ID
GROUP BY Product_ID)
DELETE FROM Stack_Example WHERE ID IN (SELECT TOP 1 ID
FROM Stack_Example
WHERE Product_Id IN ( (SELECT TOP 1 Product_ID
FROM Stack_Example
GROUP BY Product_ID
HAVING COUNT(Product_ID)>1)))

Answer 1

First update your table with total amount of products with same price
with cte as (
select
Product_ID, Price, Quantity = sum(Quantity)
from
Stack_Example
group by Product_ID, Price
)
update s
set s.Quantity = c.Quantity
from
Stack_Example s
join cte c on s.Product_ID = c.Product_ID and s.Price = c.Price
Then run another script to delete duplicate rows
with cte as (
select
*, row_number() over (partition by Product_ID, Price order by Product_ID) rn
from
Stack_Example
)
delete from cte where rn > 1

Answer 2

I'm a bit unclear - but couldn't you just create a view with the aggrgates?
Anyhow.....
Not sure why you would do this but...you could insert the aggregated values and then delete the older ones....as per below.
DECLARE #MaxId INT;
DECLARE #ProductId = 25;
--GET THE MAX ID OF PRODUCT IN QUESTION
SELECT #MaxId = MAX(ID) FROM Stack_Example WHERE Product_Id = #ProductId;
--INSERT THE AGGREGATE VALUES INTO TABLE
INSERT INTO Stack_Example
SELECT #MaxId + 1, #ProductId, Price, SUM(Quantity)
FROM Stack_Example
WHERE
Product_Id = #ProductId
GROUP BY
#MaxId + 1, [Product_ID], [Price];
--DELETE THE PRE-AGGREGATE VALUES
DELETE FROM Stack_Example WHERE ProductId = #ProductId and Id <= #MaxId;

Answer 3

Well, I used aggregates and additional temporary table to achieve that:
--group records and insert them into temporary table
select distinct
Min(id) over (partition by product_id, price) [ID],
Product_id,
sum(Quantity) over (partition by product_id, price) [Quantity],
Price
into #new_stack_example
from #Stack_Example
--delete old values
delete #Stack_example
--insert new values
insert into #Stack_example
select * from #new_stack_example
First SELECT statement reflects your logic:
So my problem here is i need to group those items by Price, Product_Id and SUM(Quantity).
But instead of grouping, I use window functions and then select distinct records.

Answer 4

Check this:
UPDATE Stack_Example SET Quantity = a.Quantity
from ( select Product_ID,sum(Quantity) Quantity
from Stack_Example Group by Product_ID) a
where Stack_Example.Product_ID=a.Product_ID
;with cte as (
select *,ROW_NUMBER () over (partition by product_id order by product_id) rn
from Stack_Example)
delete from cte where rn > 1