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mysql> CREATE TABLE tmw_maps(id tinyint primary key auto_increment, map text not
 null, index(id));
Query OK, 0 rows affected (0.01 sec)

mysql> show keys from tmw_maps\G
*************************** 1. row ***************************
       Table: tmw_maps
  Non_unique: 0
    Key_name: PRIMARY
Seq_in_index: 1
 Column_name: id
   Collation: A
 Cardinality: 0
    Sub_part: NULL
      Packed: NULL
        Null: 
  Index_type: BTREE
     Comment: 
*************************** 2. row ***************************
       Table: tmw_maps
  Non_unique: 1
    Key_name: id
Seq_in_index: 1
 Column_name: id
   Collation: A
 Cardinality: NULL
    Sub_part: NULL
      Packed: NULL
        Null: 
  Index_type: BTREE
     Comment: 
2 rows in set (0.00 sec)