Summarizing Only Rows with given criteria - tsql

Question

all!
Given the following table structure
DECLARE #TempTable TABLE
(
idProduct INT,
Layers INT,
LayersOnPallet INT,
id INT IDENTITY(1, 1) NOT NULL,
Summarized BIT NOT NULL DEFAULT(0)
)
and the following insert statement which generates test data
INSERT INTO #TempTable(idProduct, Layers, LayersOnPallet)
SELECT 1, 2, 4
UNION ALL
SELECT 1, 2, 4
UNION ALL
SELECT 1, 1, 4
UNION ALL
SELECT 2, 2, 4
I would like to summarize only those rows (by the Layers only) with the same idProduct and which will have the sum of layers equal to LayersOnPallet.
A picture is worth a thousand words:
From the picture above, you can see that only the first to rows were summarized because both have the same idProduct and the sum(layers) will be equal to LayersOnPallet.
How can I achieve this? It's there any way to do this only in selects (not with while)?
Thank you!

Answer 1

Perhaps this will do the trick. Note my comments:
-- your sample data
DECLARE #TempTable TABLE
(
idProduct INT,
Layers INT,
LayersOnPallet INT,
id INT IDENTITY(1, 1) NOT NULL,
Summarized BIT NOT NULL DEFAULT(0)
)
INSERT INTO #TempTable(idProduct, Layers, LayersOnPallet)
SELECT 1, 2, 4 UNION ALL
SELECT 1, 2, 4 UNION ALL
SELECT 1, 1, 4 UNION ALL
SELECT 2, 2, 4;
-- an intermediate temp table used for processing
IF OBJECT_ID('tempdb..#processing') IS NOT NULL DROP TABLE #processing;
-- let's populate the #processing table with duplicates
SELECT
idProduct,
Layers,
LayersOnPallet,
rCount = COUNT(*)
INTO #processing
FROM #tempTable
GROUP BY
idProduct,
Layers,
LayersOnPallet
HAVING COUNT(*) > 1;
-- Remove the duplicates
DELETE t
FROM #TempTable t
JOIN #processing p
ON p.idProduct = t.idProduct
AND p.Layers = t.Layers
AND p.LayersOnPallet = t.LayersOnPallet
-- Add the new, updated record
INSERT #TempTable
SELECT
idProduct,
Layers * rCount,
LayersOnPallet, 1
FROM #processing;
DROP TABLE #processing; -- cleanup
-- Final output
SELECT idProduct, Layers, LayersOnPallet, Summarized
FROM #TempTable;
Results:
idProduct Layers LayersOnPallet Summarized
----------- ----------- -------------- ----------
1 4 4 1
1 1 4 0
2 2 4 0