Array
(
    [id] => 1
    [select_type] => PRIMARY
    [table] =>
    [type] => ALL
    [possible_keys] =>
    [key] =>
    [key_len] =>
    [ref] =>
    [rows] => 2
    [Extra] => Using where
)
Array
(
    [id] => 4
    [select_type] => DEPENDENT SUBQUERY
    [table] => p
    [type] => ref
    [possible_keys] => topic_id,poster_id,tid_post_time
    [key] => tid_post_time
    [key_len] => 3
    [ref] => sub.topic_id
    [rows] => 1
    [Extra] => Using where
)
Array
(
    [id] => 2
    [select_type] => DERIVED
    [table] => t
    [type] => index
    [possible_keys] =>
    [key] => topic_approved
    [key_len] => 1
    [ref] =>
    [rows] => 146484
    [Extra] => Using where; Using index
)
Array
(
    [id] => 3
    [select_type] => DEPENDENT SUBQUERY
    [table] => p
    [type] => ref
    [possible_keys] => topic_id,poster_id,tid_post_time
    [key] => tid_post_time
    [key_len] => 3
    [ref] => db_name.t.topic_id
    [rows] => 1
    [Extra] => Using where
)