Joins with nulls

I've read that performing joins with tables that have null values in some attributes is a dangerous operation, but no example was given. I think that this only can happen if you try to join based on the attributes that can have two null values, due to the problem of how to interpret null values (are two null values equal?). Can this also happen in other circumstances?.

Thanks in advance

P.S. Sorry for so many messages, but I've been studying the normalization theory deeply and some doubts have arised. Received on Thu Nov 14 2002 - 22:37:46 CET