INCLUDE equivalent in Oracle

Question

In SQL server you can write

create index indx on T1 (A,B) INCLUDE (C,D,E) 

Is there a way to do the same thing in Oracle?

Answer 1

Refs:
http://msdn.microsoft.com/en-us/library/ms190806.aspx
http://www.dba-oracle.com/t_garmany_easysql_btree_index.htm

This answer is here to point out that SQL Server Included columns do not store the INCLUDED columns at the key levels, only at the leaf level. If you include 4 columns, they get stored as data in a block on the leaf level.

Creating them as additional parts of a composite index breaks the index into more levels instead.

As composite index (A,B,C)

  Level1   Level2   Leaf
           (Branch)
  A1
           B1
                    C1
           B2
                    C3
           B3
                    C6
                    C7
  A2

As index (A) include (B,C)

  Level1    Leaf
  A1        B1,C1 | B2,C3 | B3,C6 | B3,C7
  A2        null,null

The difference in storage structure (which affects performance) is the reason why they are introduced as INCLUDED columns, otherwise there would be no reason to introduce this new feature.