mysql创建联合索引

mysql> desc books;
+--------+-------------+------+-----+---------+-------+
| Field  | Type        | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| name   | varchar(30) | YES  | UNI | NULL    |       |
| author | varchar(20) | YES  |     | NULL    |       |
| jb     | varchar(20) | YES  |     | NULL    |       |
+--------+-------------+------+-----+---------+-------+
3 rows in set (3.20 sec)

mysql> alter table books add index `books_index_name` (`name`,`author`);
Query OK, 0 rows affected (1 min 14.00 sec)
Records: 0  Duplicates: 0  Warnings: 0