TSQL, join to multiple fields of which one could be NULL

Question

I have a simple query:

SELECT * FROM Products p 
LEFT JOIN SomeTable st ON st.SomeId = p.SomeId AND st.SomeOtherId = p.SomeOtherId

So far so go

Answer 1

From Undocumented Query Plans: Equality Comparisons.

SELECT *
FROM   Products p
       LEFT JOIN SomeTable st
         ON st.SomeOtherId = p.SomeOtherId
            AND EXISTS (SELECT st.SomeId INTERSECT SELECT p.SomeId)