SQL query:
 EXPLAIN
  SELECT p.author_id member_id,
         m.name member_name,
         COUNT(p.pid) posts
    FROM forum_posts p
         INNER JOIN forum_members m
                    ON p.author_id = m.member_id
         INNER JOIN forum_topics t
                    ON t.forum_id = 120
                       AND t.tid = p.topic_id
   WHERE p.author_id != 0
         AND p.new_topic = 0
GROUP BY p.author_id
ORDER BY posts DESC
   LIMIT 1
Rows: 3
Result:

id	select_type	table	type    possible_keys			key		key_len	ref			rows	Extra
1	SIMPLE		t	ref	PRIMARY,forum_id,last_post	forum_id	2	const			25420	Using temporary; Using filesort
1	SIMPLE		p	ref	author_id,topic_id		topic_id	4	wmonline2.t.tid		5	Using where
1	SIMPLE		m	eq_ref	PRIMARY				PRIMARY		3	wmonline2.p.author_id	1

-------------------------------------------------------------------------------

SQL query:
DESCRIBE forum_members
Rows: 74
Result:

Field 	Type 	Null 	Key 	Default 	Extra
member_id	mediumint(8)	NO	PRI	NULL	auto_increment
name	varchar(32)	NO
member_group_id	smallint(3)	NO	MUL	0
email	varchar(150)	NO
joined	int(10)	NO	 	0
ip_address	varchar(16)	NO	MUL
posts	mediumint(7)	YES	 	0
title	varchar(64)	YES	 	NULL
allow_admin_mails	tinyint(1)	YES	 	NULL
time_offset	varchar(10)	YES	 	NULL
hide_email	varchar(8)	YES	 	NULL
email_pm	tinyint(1)	YES	 	NULL
email_full	tinyint(1)	YES	 	NULL
skin	smallint(5)	YES	 	NULL
warn_level	int(10)	YES	 	NULL
warn_lastwarn	int(10)	NO	 	0
language	varchar(32)	YES	 	NULL
last_post	int(10)	YES	 	NULL
restrict_post	varchar(100)	NO	 	0
view_sigs	tinyint(1)	YES	 	1
view_img	tinyint(1)	YES	 	1
view_avs	tinyint(1)	YES	 	1
view_pop	tinyint(1)	YES	 	1
bday_day	int(2)	YES	MUL	NULL
bday_month	int(2)	YES	MUL	NULL
bday_year	int(4)	YES	 	NULL
msg_count_new	int(2)	NO	 	0
msg_count_total	int(3)	NO	 	0
msg_count_reset	int(1)	NO	 	0
msg_show_notification	int(1)	NO	 	0
misc	varchar(128)	YES	 	NULL
last_visit	int(10)	YES	 	0
last_activity	int(10)	YES	 	0
dst_in_use	tinyint(1)	YES	 	0
view_prefs	varchar(64)	YES	 	-1&-1
coppa_user	tinyint(1)	YES	 	0
mod_posts	varchar(100)	NO	 	0
auto_track	varchar(50)	YES	 	0
org_perm_id	varchar(255)	YES
temp_ban	varchar(100)	YES	 	0
sub_end	int(10)	NO	 	0
no_sig_lims	tinyint(1)	NO	 	0
login_anonymous	char(3)	NO	 	0&0
ignored_users	text	YES	 	NULL
mgroup_others	varchar(255)	NO
member_login_key	varchar(32)	NO
member_login_key_expire	int(10)	NO	 	0
subs_pkg_chosen	smallint(3)	NO	 	0
has_blog	tinyint(1)	NO	 	0
members_auto_dst	tinyint(1)	NO	 	1
members_cache	mediumtext	YES	 	NULL
members_disable_pm	int(1)	NO	 	0
members_display_name	varchar(255)	NO
members_seo_name	varchar(255)	NO
members_created_remote	tinyint(1)	NO	 	0
members_editor_choice	char(3)	NO	 	std
members_profile_views	int(10) unsigned	NO	 	0
members_l_display_name	varchar(255)	NO	MUL	0
members_l_username	varchar(255)	NO	MUL	0
failed_logins	text	YES	 	NULL
failed_login_count	smallint(3)	NO	 	0
has_gallery	int(1)	YES	 	0
members_pass_hash	varchar(32)	NO
members_pass_salt	varchar(5)	NO
member_banned	tinyint(1)	NO	MUL	0
identity_url	text	YES	 	NULL
member_uploader	varchar(32)	NO	 	default
members_bitoptions	int(10) unsigned	NO	MUL	0
fb_uid	bigint(20)	NO	 	0
fb_emailhash	varchar(60)	NO
fb_emailallow	int(1)	NO	 	0
fb_lastsync	int(10)	NO	 	0
members_day_posts	varchar(32)	NO	 	0,0
live_id	varchar(32)	YES	 	NULL

-------------------------------------------------------------------------------

SQL query:
DESCRIBE forum_posts
Rows: 20
Result:

Field 	Type 	Null 	Key 	Default 	Extra
append_edit	tinyint(1)	YES	 	0
edit_time	int(10)	YES	 	NULL
pid	int(10)	NO	PRI	NULL	auto_increment
author_id	mediumint(8)	NO	MUL	0
author_name	varchar(32)	YES	 	NULL
use_sig	tinyint(1)	NO	 	0
use_emo	tinyint(1)	NO	 	0
ip_address	varchar(16)	NO	MUL
post_date	int(10)	YES	MUL	NULL
icon_id	smallint(3)	YES	 	NULL
post	mediumtext	YES	 	NULL
queued	tinyint(1)	NO	 	0
topic_id	int(10)	NO	MUL	0
post_title	varchar(255)	YES	 	NULL
new_topic	tinyint(1)	YES	 	0
edit_name	varchar(255)	YES	 	NULL
post_parent	int(10)	NO	 	0
post_key	varchar(32)	NO	MUL	0
post_htmlstate	smallint(1)	NO	 	0
post_edit_reason	varchar(255)	NO

-------------------------------------------------------------------------------

SQL query:
DESCRIBE forum_topics
Rows: 31
Result:

tid	int(10)	NO	PRI	NULL	auto_increment
title	varchar(70)	NO	MUL
description	varchar(250)	YES	 	NULL
state	varchar(8)	YES	 	NULL
posts	int(10)	YES	 	NULL
starter_id	mediumint(8)	NO	MUL	0
start_date	int(10)	YES	MUL	NULL
last_poster_id	mediumint(8)	NO	 	0
last_post	int(10)	YES	MUL	NULL
icon_id	tinyint(2)	YES	 	NULL
starter_name	varchar(255)	YES	 	NULL
last_poster_name	varchar(255)	YES	 	NULL
poll_state	varchar(8)	YES	 	NULL
last_vote	int(10)	YES	 	NULL
views	int(10)	YES	 	0
forum_id	smallint(5)	NO	MUL	0
approved	tinyint(1)	NO	 	0
author_mode	tinyint(1)	YES	 	NULL
pinned	tinyint(1)	NO	 	0
moved_to	varchar(64)	YES	 	NULL
total_votes	int(5)	NO	 	0
topic_hasattach	smallint(5)	NO	 	0
topic_firstpost	int(10)	NO	MUL	0
topic_queuedposts	int(10)	NO	 	0
topic_rating_total	smallint(5) unsigned	NO	 	0
topic_rating_hits	smallint(5) unsigned	NO	 	0
topic_open_time	int(10)	NO	 	0
topic_close_time	int(10)	NO	 	0
title_seo	varchar(250)	NO
seo_last_name	varchar(255)	NO
seo_first_name	varchar(255)	NO