CREATE TABLE `IBMS_Mart_myisam` (
 `minor_present_contributors` char( 24 ) DEFAULT NULL ,
 `minor_specific_contributors` char( 24 ) DEFAULT NULL ,
 `CL` char( 13 ) NOT NULL DEFAULT '0000000000000',
 `AL` char( 13 ) NOT NULL DEFAULT '0000000000000',
 `SX` char( 6 ) NOT NULL DEFAULT 'AAAAAA',
 `Less_18` char( 1 ) DEFAULT NULL ,
 `Less_14` char( 1 ) DEFAULT NULL ,
 `minor_specific` char( 1 ) DEFAULT NULL ,
 UNIQUE KEY `IBMS_Mart_CL` ( `CL` ) USING BTREE,
 KEY `IBMS_Mart_AL` ( `AL` ) USING BTREE,
 KEY `IBMS_Mart_AL_SX` ( `AL` , `SX` ) USING BTREE
) ENGINE = MyISAM

LOAD DATA CONCURRENT LOCAL INFILE 'IBMS_Mart.csv' INTO TABLE IBMS_Mart_myisam fields terminated by ',' optionally enclosed by '"' lines terminated by '\n';

phpMyAdmin:
Data  	6,829.9  	MiB
Index 	3,113.0 	MiB
Total 	9,942.9 	MiB

mysql> SELECT CL FROM IBMS_Mart_myisam WHERE CL=1234567891234;
Empty set (51.85 sec)


mysql> SHOW INDEX FROM IBMS_Mart_myisam;
+------------------+------------+-----------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| Table            | Non_unique | Key_name        | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment |
+------------------+------------+-----------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| IBMS_Mart_myisam |          0 | IBMS_Mart_CL    |            1 | CL          | A         |    85258537 |     NULL | NULL   |      | BTREE      |         |
| IBMS_Mart_myisam |          1 | IBMS_Mart_AL    |            1 | AL          | A         |    42629268 |     NULL | NULL   |      | BTREE      |         |
| IBMS_Mart_myisam |          1 | IBMS_Mart_AL_SX |            1 | AL          | A         |    42629268 |     NULL | NULL   |      | BTREE      |         |
| IBMS_Mart_myisam |          1 | IBMS_Mart_AL_SX |            2 | SX          | A         |    42629268 |     NULL | NULL   |      | BTREE      |         |
+------------------+------------+-----------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
4 rows in set (0.00 sec)