Finding duplicate values in multiple rows in SQL Server table - sql

Question

I have a SQL Server database table with this sample data:
ProductID GenericID MG
---------------------------------
1 1 2g
1 2 5g
2 2 5g
3 1 2g
3 2 5g
4 1 2g
5 1 2g
5 3 7g
6 2 5g
7 1 2g
8 1 2g
I want to find out the query to select data
if I select 'ProductID=1' then the query should check what 'GenericID' are associated with 'ProductID=1'
In above data case if user select 'ProductID=1' then query will check 'GenericID=1' and 2 are associated with 'ProductID=1'.
Then after I want to go through all rows and select those rows who has the same Unique 'ProductID' and also having only 'GenericID=1 and 2'.
as in above case the final output will be as shown below....
I select 'ProductID=1' and output has four rows, because only ProductId 3 has same 'GenericID' as were of 'ProductId=1'
If I select only ProductId=1 then I want to get all the rows with the same exact set of GenericID values as ProductID=1, which is the set { 1, 2 } in my sample data. I am struggling with the query logic.
For example - I select ProductID=1, this is the output that I want is as follows, because ProductID 3 has the same set of GenericID values as ProductID 1.
ProductID GenericID MG
-------------------------------
1 1 2g
1 2 5g
3 1 2g
3 2 5g
GenericID can be on or multiple dynamic values.
Another example - if I select ProductID=7, this is the output I want:
In this example - It will only get those results that are having only GenericID=1 because ProductID=7 has only GenericID=1. any set of productID which is having 'GenericID=1' and also that set includes other 'GenericID' will be neglected.
ProductID GenericID MG
------------------------------
7 1 2g
8 1 2g
4 1 2g
I need to find out the query to select the required output.
I want all of the products that have the same set of generic id's as the predicate product.

Answer 1

How about
SELECT *
FROM yourtable
WHERE
GenericID in (SELECT GenericID FROM yourtable WHERE ProductID=1)
Update:
If the whole set of GenericIDs needs to match, this should work (assuming ProductID, GenericID is unique):
WITH yourtable_gids AS (
SELECT
ProductID,
STRING_AGG(GenericID, ',') WITHIN GROUP (ORDER BY GenericID) as GenericIDs
FROM yourtable
GROUP BY ProductID
)
SELECT y.*
FROM yourtable y
JOIN yourtable_gids yg ON y.ProductID=yg.ProductID
WHERE
yg.GenericIDs in (SELECT GenericIDs FROM yourtable_gids WHERE ProductID=1)

Answer 2

So if i interpret the question right it's
I select on a product Id, and want to additionaly have every product with the same generic IDs as the ones I got.
select * from products
where productID = X
or genericId in (select genericId from products where product ID = X)
This should be the answer if I got your question right.