order by 시 속도 단축 방법 질문 드립니다.

테이블은 아래와 같습니다.

CREATE TABLE U_MEMBER (
 MEMBER_SEQ INT(8) NOT NULL AUTO_INCREMENT,  
 MEMBER_ID VARCHAR(32) NOT NULL,   
 MEMBER_NAME  VARCHAR(32) NOT NULL,   
 MEMBER_PASSWORD VARCHAR(24) NOT NULL, 
 STATION_CODE INT(8),     
 DEPT_CODE INT(8),     
 GRADE_CODE INT(8),     
 EMAIL  VARCHAR(64),
  PRIMARY KEY(MEMBER_SEQ, MEMBER_ID)
) ENGINE=MYISAM DEFAULT CHARSET=EUCKR;

CREATE TABLE U_GRADE (
 GRADE_CODE  VARCHAR(32) NOT NULL, 
 GRADE_NAME VARCHAR(32),  
 DISP_ORDER INT(4),   
 PRIMARY KEY(GRADE_CODE) 
) ENGINE=MYISAM DEFAULT CHARSET=EUCKR;

CREATE TABLE U_DEPT (
 DEPT_CODE   VARCHAR(32) NOT NULL, 
 DEPT_NAME   VARCHAR(64),  
 PRIMARY KEY(DEPT_CODE)
) ENGINE=MYISAM DEFAULT CHARSET=EUCKR;

U_MEMBER 테이블에 약 3만건의 데이터가 들어간 경우,

아래 질의를 하면 0.094 정도의 속도가 나옵니다.
 

 SELECT
 MEM.MEMBER_SEQ SEQ,              
 MEM.MEMBER_ID ID,              
 MEM.MEMBER_NAME NAME, 
 GRADE.GRADE_NAME,
 MEM.EMAIL EMAIL  
 FROM
 U_MEMBER MEM,
 U_GRADE GRADE
 WHERE
 MEM.MEMBER_ID = MEM.MEMBER_ID
 AND MEM.GRADE_CODE = GRADE.GRADE_CODE
 ORDER BY MEM.MEMBER_NAME ASC LIMIT 0, 6;

index는 아래와 같습니다. 걸어준게 없죠.

이렇게 저렇게 걸어줘도 속도가 나오지 않아서.

직위도 그렇고, 부서도 나중에 select에 추가해야 되는데 속도를 좀더 빨리 할 수는 없는지.

부탁드립니다.
mysql> SHOW INDEX FROM U_MEMBER;
+----------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| Table    | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment |
+----------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| U_MEMBER |          0 | PRIMARY  |            1 | MEMBER_SEQ  | A         |        NULL |     NULL | NULL   |      | BTREE      |         |
| U_MEMBER |          0 | PRIMARY  |            2 | MEMBER_ID   | A         |       30000 |     NULL | NULL   |      | BTREE      |         |
+----------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
2 rows in set (0.00 sec)

mysql> show INDEX FROM U_GRADE;
+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| Table   | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part| Packed | Null | Index_type | Comment |
+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| U_GRADE |          0 | PRIMARY  |            1 | GRADE_CODE  | A         |           5 |     NULL| NULL   |      | BTREE      |         |
+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
1 row in set (0.00 sec)