7-29. B-Tree index leaf entry characteristics

In a B-tree index on a nonpartitioned table:

• Key value are repeated if there are multiple rows that have the same key value unless the index is compressed
• There is no index entry corresponding to a row that has all key columns that are NULL. Therefore, a WHERE clase specifying NULL will always result in a full table scan.
• Restricted ROWID is used to point to the rows of the table because all rows belong to the same segment.