Index for nullable column

Question

I have an index on a nullable column and I want to select all it\'s values like this:

SELECT e.ename 
FROM   emp e;

In the explain plan I s

Answer 1

I am not sure the first query is pertinent in terms of index usage, at least the second could.

Anyway, while it is true that you cannot index a column containing a null value, there are ways to do it like for example:

create index MY_INDEX on emp(ename, 1);

notice the , 1) at the end which does the trick.