Pivot with Group by on SQL - sql-server

Question

I'm create sql syntax which create pivot Group By Product based on Category
CREATE TABLE #Product ( Product varchar(10),Category varchar(10),Stock int)
INSERT INTO #Product Values ('Item A','CatA',10)
INSERT INTO #Product Values ('Item A','CatB',5)
INSERT INTO #Product Values ('Item B','CatA',3)
INSERT INTO #Product Values ('Item B','CatB',5)
INSERT INTO #Product Values ('Item B','CatC',7)
INSERT INTO #Product Values ('Item B','CatD',10)
SELECT *
FROM
(
SELECT Product,Category,Stock
FROM #Product A
) src
pivot
(
SUM(Stock)
for Category in ([CatA], [CatB], [CatC],[CatD])
) piv;
DROP TABLE #Product
Result of Query
Product CatA CatB CatC CatD
Item A 10 5 NULL NULL
Item B 3 5 7 10
Result trying to achieve is
Product Cat1 Stock1 Cat2 Stock2 Cat3 Stock3 Cat4 Stock4
Item A CatA 10 CatB 5 CatC 0 CatD 0
Item B CatA 3 CatB 5 CatC 7 CatD 10
Thanks for the help

Answer 1

You need to create all combinations of Product and Category first. Then do a LEFT JOIN on #Product to get the Stock. Finally, use the result to pivot the data.
Since I'm not familiar with the PIVOT command, I used another technique called Dynamic Crosstab
DECLARE #sql NVARCHAR(MAX) = N'';
SELECT #sql =
'SELECT
Product' + CHAR(10);
SELECT #sql = #sql +
STUFF((
SELECT
' ,MAX(CASE WHEN RN = ' + CONVERT(VARCHAR(3), t.RN) + ' THEN Category END) AS ' + QUOTENAME('Cat' + CONVERT(VARCHAR(3), t.RN)) + CHAR(10) +
' ,MAX(CASE WHEN RN = ' + CONVERT(VARCHAR(3), t.RN) + ' THEN Stock END) AS ' + QUOTENAME('Stock' + CONVERT(VARCHAR(3), t.RN)) + CHAR(10)
FROM (
SELECT DISTINCT
RN = ROW_NUMBER() OVER(PARTITION BY Product ORDER BY(SELECT NULL))
FROM #Product
) t
FOR XML PATH('')
), 1, 1, ' ');
SELECT #sql = #sql +
'FROM(
SELECT
p1.Product,
p1.Category,
Stock = ISNULL(p2.Stock, 0),
RN = ROW_NUMBER() OVER(PARTITION BY p1.Product ORDER BY p1.Category)
FROM (
SELECT
t1.Product, t2.Category
FROM (
SELECT DISTINCT Product FROM #Product
) t1
CROSS JOIN (
SELECT DISTINCT Category FROM #Product
) t2
) p1
LEFT JOIN #Product p2
ON p1.Product = p2.Product
AND p1.Category = p2.Category
)t
GROUP BY Product;';
PRINT #sql;
EXEC sp_executesql #sql;
ONLINE DEMO