constrain with MATCH full and NULL values in referenced table

I am creating a table that has 2 values in it which are keys pointing to 2
other tables. I need for the UNIQUE combination of these 2 keys to exist in
a fourth table. It has been recommended to use a foreign key constraint with
the MATCH FULL parameter. 

Here is my question, does this deal with NULLS in the 4th table? I am
concerned that this constraint might fail to reject an entry if one, or both
of the 2 key values being inserted in the table are NULLS,.



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