Does "UNIQUE" Also Create An "INDEX"

[Volitics]

Can anyone tell me if I designate a column as "UNIQUE" in the MySQL database does MySQL also index that column?

In other words, if the "UserName" column is designated as "UNIQUE" in order to make the searches go faster do I also need to designate the "UserName" column as an "INDEX" key?

For example if I designate the UserName column as UNIQUE then there could be only one each of the following six usernames:

Jones2
Smith#2
Larkin54
Aaron1
Hudson21
Jarrettxyz

However, if I designate the UserName column as UNIQUE does MySQL also place the usernames in alphabetical order like so:

Aaron1
Hudson21
Jarrettxyz
Jones2
Larkin54
Smith#2

in order to make the searches faster?

Thanks.

[LordShryku]

Unique is a type of index, so if you specify a unique contraint on a field, yes it does create an index.
http://www.mysql.com/doc/en/MySQL_indexes.html

[Volitics]

LordShryku

Thank you for the help.

Volitics