MS-SQL Grouping and counting query - sql

Question

So I have a table and the columns are Product and ProductGroupID.
Every Product can be in 1 or more groups as shown in this example:
+-------+--------------+
|product|ProductGroupId|
+-------+--------------+
| 10 | 2 |
| 10 | 9 |
| 10 | 4 |
| 10 | 7 |
| 20 | 7 |
| 30 | 4 |
| 40 | 1 |
| 50 | 11 |
| 50 | 12 |
| 60 | 2 |
| 70 | 9 |
| 80 | 11 |
| 90 | 12 |
| 100 | 13 |
+-------+--------------+
For every product I need to get it's group or groups and to bring the number of product which are in those groups.
For example product 10 is in groups 2,4,9,7 so I need to count all the products that are in those groups, in this case 5 (for count of products 10,60,70,30,20).
I attach the full desired outcome for this example.
https://i.stack.imgur.com/XTa4R.png
Any suggestion how to do this in ms-sql?
Thnaks!

Answer 1

If I understood it correctly this will work for you.
Schema from your image:
CREATE TABLE #PRODUCTS (PRODUCT INT, PRODUCTGROUP_ID INT)
INSERT INTO #PRODUCTS
SELECT 10,2
UNION ALL
SELECT 10,9
UNION ALL
SELECT 10,4
UNION ALL
SELECT 10,7
UNION ALL
SELECT 20,7
UNION ALL
SELECT 30,4
UNION ALL
SELECT 40,1
UNION ALL
SELECT 50,11
UNION ALL
SELECT 50,12
UNION ALL
SELECT 60,2
UNION ALL
SELECT 70,9
UNION ALL
SELECT 80,11
UNION ALL
SELECT 90,12
UNION ALL
SELECT 100,13
Now do a Self Join with GroupId on condition
SELECT P.PRODUCT, COUNT(DISTINCT G.PRODUCT) Linked_GroupProducts
FROM #PRODUCTS P
INNER JOIN #PRODUCTS G ON P.PRODUCTGROUP_ID = G.PRODUCTGROUP_ID
GROUP BY P.PRODUCT
And the result will be
+---------+----------------------+
| PRODUCT | Linked_GroupProducts |
+---------+----------------------+
| 10 | 5 |
| 20 | 2 |
| 30 | 2 |
| 40 | 1 |
| 50 | 3 |
| 60 | 2 |
| 70 | 2 |
| 80 | 2 |
| 90 | 2 |
| 100 | 1 |
+---------+----------------------+