Hi, I am joining two or more tables on the column that has quite a number of nulls, assuming 'a.key = b.key' to be a valid expression even when both operands are NULLs. The result set is way smaller that I expect. Could that be because the two NULLs do not match? I guess there are two possible ways to treat the NULL = NULL problem. One is to say, "Don't know. There is no information to say whether this is true or false". The second is to say, "Yes, these two entities are the same. They are equally undetermined". The function I want to achieve is: 'a.key = b.key' OR ((a.key IS NULL) AND (b.key IS NULL)) Isn't it the way it's wired? --Gene
