Question

For reasons beyond my control, I need to join two tables and I need null values to match. The best option I could think of was to spit out a UUID and use that as my comparison value but it seems ugly

SELECT * FROM T1 JOIN T2 ON nvl(T1.SOMECOL,'f44087d5935dccbda23f71f3e9beb491') = 
   nvl(T2.SOMECOL,'f44087d5935dccbda23f71f3e9beb491')

How can I do better? This is on Oracle if it matters, and the context is an application in which a batch of user-uploaded data has to be compared to a batch of existing data to see if any rows match. In retrospect we should have prevented any of the join columns in either data set from containing nulls, but we didn’t and now we have to live with it.

Edit: To be clear, I’m not only concerned with nulls. If the columns are not null I want them to match on their actual values.

Answer 1

Maybe this would work, but I’ve never actually tried it:

SELECT * 
FROM T1 JOIN T2 
ON T1.SOMECOL = T2.SOMECOL OR (T1.SOMECOL IS NULL AND T2.SOMECOL IS NULL)