Q:

SQL - Return rows matching all values from a joined table

Title might not be massively helpful on this one so I'll try and explain it as best I can. 
Assume two tables. 
Product (ProductID, Name)
ProductCategory (ID, ProductID, CategoryID)

and a third temporary table containing a list of CategoryIDs to match. 
MatchTable(CategoryID)

I want to use the contents of MatchTable to return the products that have all of the associated categories.    IE. 
Product 1: Associated with categories 1 and 2. 
Product 2: Associated with categories 2 and 3. 
Product 3: Associated with categories 1, 2 and 3. 

If MatchTable contains 1 and 2, I want to return products 1 and 3 because they match the criteria.   If MatchTable contains 2 then all products would be returned. 
The code for returning a product that matches any of the values in MatchTable is easy, but I can't seem to get the syntax right for the products that match all. 

A:

Guess I'd test a match count vs rows in the matchtable
select p.ProductID, max(p. Name)
from Product p
inner join ProductCategory c on c.ProductID = p.ProductID
inner join MatchTable m on m.CategoryID = c.CategoryID
group by p.ProductID
having COUNT(*) = (select COUNT(*) from MatchTable)

See fiddle

