CREATE INDEX is mapped to an ALTER TABLE statement to create indexes. See Section 12.1.2, “ALTER TABLE Syntax”. CREATE INDEX cannot be used to create a PRIMARY KEY; use ALTER TABLE instead. For more information about indexes, see Section 7.4.5, “How MySQL Uses Indexes”.
http://dev.mysql.com/doc/refman/5.0/en/mysql-indexes.html

CREATE UNIQUE INDEX keyword ON `eEcho`.`keyword` (keyword(128));

http://dev.mysql.com/doc/refman/5.0/en/create-index.html