SQL Server pivot query - questions - sql

Question

I have a table with 3 columns: order_id, product_id, product_count
The first column is an order passed by a client, the second is the product unique id and the third is the quantity of a product bought in an order.
I want to create a matrix of order_id / product_id with number of items bought.
As a result I would like to have something that looks like this:
If I make this request:
SELECT *
FROM
(SELECT
[order_id], [prod_id], [product_count]
FROM mydb.dbo.mytable) QueryResults
PIVOT
(SUM([product_count])
FOR [prod_id] IN ([21], [22], [23])
) AS PivotTable
My issue is that I have more than 200 different products to retrieve. Is there a way to make it without entering all values?

Answer 1

I'd written this and was testing when BICube posted his comment - and yes, this is another dynamic Pivot. You had the basic code - all you need to do is to
Build a variable with the column name list e.g., ColList = '[21],[22],[23]'
Use this variable in the PIVOT to provide the column list - but note you then need to make the whole statement into Dynamic SQL.
Here is the answer I wrote (Note I just made up order data rather than transcribing from your image).
CREATE TABLE #MyTable (Order_ID int, Prod_ID int, Product_Count int);
INSERT INTO #MyTable (Order_ID, Prod_ID, Product_Count)
VALUES
(100, 1, 15),
(100, 2, 12),
(100, 5, 17),
(101, 3, 10),
(101, 4, 11),
(102, 6, 12),
(102, 1, 16);
SELECT * FROM #MyTable;
DECLARE #ColList nvarchar(max) = N''
SELECT #ColList += N',' + QUOTENAME(LTRIM(STR(Prod_ID)))
FROM (SELECT DISTINCT Prod_ID FROM #MyTable) A;
SET #ColList = STUFF(#ColList,1,1,''); -- Remove leading comma
DECLARE #PivotSQL nvarchar(max);
SET #PivotSQL =
N'SELECT * FROM (
SELECT
[Order_ID],
[prod_id],
[product_count]
FROM #MyTable
) QueryResults
PIVOT (
SUM([product_count])
FOR [prod_id]
IN (' + #ColList + N')
) AS PivotTable;'
EXEC (#PivotSQL);
And here are the results
Order_ID 1 2 3 4 5 6
100 15 12 NULL NULL 17 NULL
101 NULL NULL 10 11 NULL NULL
102 16 NULL NULL NULL NULL 12

Answer 2

Based on #seanb answer that saved me, I tried to replace the NULL values with 0. I understood the principle (the base). Here is how I updated the SQL request to replace the NULL values.
DECLARE #DynamicPivotQuery AS NVARCHAR(MAX),
#PivotColumnNames AS NVARCHAR(MAX),
#PivotSelectColumnNames AS NVARCHAR(MAX)
--Get distinct values of the PIVOT Column
SELECT #PivotColumnNames= ISNULL(#PivotColumnNames + ',','') + QUOTENAME(prod_id)
FROM (SELECT DISTINCT prod_id FROM #MyTable) AS prod_id
--Get distinct values of the PIVOT Column with isnull
SELECT #PivotSelectColumnNames
= ISNULL(#PivotSelectColumnNames + ',','')
+ 'ISNULL(' + QUOTENAME(prod_id) + ', 0) AS '
+ QUOTENAME(prod_id)
FROM (SELECT DISTINCT prod_id FROM #MyTable) AS prod_id
--Prepare the PIVOT query using the dynamic
SET #DynamicPivotQuery =
N'SELECT order_id, ' + #PivotSelectColumnNames + '
FROM #MyTable
PIVOT(SUM(product_count)
FOR prod_id IN (' + #PivotColumnNames + ')) AS PivotTable'
--Execute the Dynamic Pivot Query
EXEC sp_executesql #DynamicPivotQuery