mysql explain select actor_id from actor order by actor_id \g *************************** 1. row *************************** id: 1 select_type: simple table: actor type: index possible_keys: null key: primary key_len: 4 ref: null rows: 4 e
mysql> explain select actor_id from actor order by actor_id \g
*************************** 1. row ***************************
           id: 1
 select_type: simple
        table: actor
         type: index
possible_keys: null
          key: primary
      key_len: 4
          ref: null
         rows: 4
        extra: using index
1 row in set (0.00 sec)
mysql> explain select actor_id from actor order by password \g
*************************** 1. row ***************************
           id: 1
 select_type: simple
        table: actor
         type: all
possible_keys: null
          key: null
      key_len: null
          ref: null
         rows: 4
        extra: using filesort
1 row in set (0.00 sec)
mysql> explain select actor_id from actor order by name \g
*************************** 1. row ***************************
           id: 1
 select_type: simple
        table: actor
         type: index
possible_keys: null
          key: name
      key_len: 18
          ref: null
         rows: 4
        extra: using index
1 row in set (0.00 sec)