Composite Index vs. INCLUDE Covering Index in SQL Server

I understand that Composite Indexes are alwa开发者_开发知识库ys used Left to Right (e.g. if an Index was on City, State, WHERE City = "Blah" or WHERE City = "Blah" AND State = "AA" would work fine but WHERE State = "AA" would not).

Does this same principle apply to INCLUDE indexes?

Thanks in advance!

Clay

Include columns can only be used to supply columns to the SELECT portion of the query. They cannot be used as part of the index for filtering.

EDIT: To further clarify my point, consider this example:

I create a simple table and populate it:

create table MyTest (
    ID int,
    Name char(10)
)

insert into MyTest
    (ID, Name)
    select 1, 'Joe' union all
    select 2, 'Alex'

Now consider these 3 indexes and their corresponding execution plans for a simple SELECT.

select ID, Name
    from MyTest
    where Name = 'Joe'

Case 1: An index on just ID results in a TABLE SCAN.

create index idx_MyTest on MyTest(ID)

Case 2: An index on ID including name. Somewhat better because the index covers the query, but I still get a SCAN operation.

create index idx_MyTest on MyTest(ID) include (Name)

Case 3: An index on Name including ID. This is the best. The index is built on the column in my WHERE clause, so I get a SEEK operation, and the index covers the query because of the included column.

create index idx_MyTest on MyTest(Name) include (ID)

No, include fields are not ordered.

Here are some additional design considerations:

http://msdn.microsoft.com/en-us/library/ms190806.aspx