Syntax:
CREATE [UNIQUE|FULLTEXT|SPATIAL] INDEX index_name
    [index_type]
    ON tbl_name (index_col_name,...)

index_col_name:
    col_name [(length)] [ASC | DESC]

index_type:
    USING {BTREE | HASH}

In MySQL 3.22 or later, CREATE INDEX is mapped to an ALTER TABLE
statement to create indexes. See [HELP ALTER TABLE]. The CREATE INDEX
statement does not do anything prior to MySQL 3.22. For more
information about indexes, see
http://dev.mysql.com/doc/refman/4.1/en/mysql-indexes.html.
