Forum OpenACS Q&A: Response to Question about an index
you will force a full table scan. I don't know why Oracle does it that way - you'd think indexing nulls just like any other value would be useful. Also, that's for normal b-tree indexes - I'm not sure whether the same is true of bitmap indexes.select foo from my_table where bar is null
On the other hand,
will be able to use the index just fine. (Whether Oracle actually uses the index or not is at the optimizer's discretion, of course).select foo from my_table where bar is NOT null
On the inserting thing, yes, Don's correct - Oracle coerces empty string to null on inserts, and I believe updates as well. Funny, I can't remember ever needing to insert a real empty string into Oracle. Offhand, I can't think of a good way to do that.