如何提高查询执行性能

以下查询需要花费时间（2.3s）才能执行。

SELECT *, COUNT(c2.id) AS c2__0 
FROM countryMaster c, stateMaster s, cityMaster c2, categoryMaster c3, categoryMaster c4, product p 
INNER JOIN user u ON ((u.id = p.user_id AND u.is_active = 1))
WHERE (p.category_id = c4.id 
AND c2.id = p.x_area_id
AND c2.parent_id = s.id 
AND s.parent_id = c.id AND c3.id IN ('1271')
AND c4.rgt = (c4.lft + 1)
AND c4.lft BETWEEN c3.lft AND c3.rgt AND p.status = 1)
GROUP BY c.id;


Explain:    
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: c3
         type: const
possible_keys: PRIMARY,lft_rgt_inx
          key: PRIMARY
      key_len: 4
          ref: const
         rows: 1
        Extra: Using temporary; Using filesort
*************************** 2. row ***************************
           id: 1
  select_type: SIMPLE
        table: p
         type: ALL
possible_keys: INX_cmp_sx,status
          key: NULL
      key_len: NULL
          ref: NULL
         rows: 29958
        Extra: Using where
*************************** 3. row ***************************
           id: 1
  select_type: SIMPLE
        table: c4
         type: eq_ref
possible_keys: PRIMARY,lft_rgt_inx
          key: PRIMARY
      key_len: 4
          ref: yozoa1_live.p.category_id
         rows: 1
        Extra: Using where
*************************** 4. row ***************************
           id: 1
  select_type: SIMPLE
        table: u
         type: eq_ref
possible_keys: PRIMARY,is_active
          key: PRIMARY
      key_len: 4
          ref: yozoa1_live.p.user_id
         rows: 1
        Extra: Using where
*************************** 5. row ***************************
           id: 1
  select_type: SIMPLE
        table: c2
         type: eq_ref
possible_keys: PRIMARY,parent_id
          key: PRIMARY
      key_len: 4
          ref: yozoa1_live.p.x_area_id
         rows: 1
        Extra: 
*************************** 6. row ***************************
           id: 1
  select_type: SIMPLE
        table: s
         type: eq_ref
possible_keys: PRIMARY,parent_id
          key: PRIMARY
      key_len: 4
          ref: yozoa1_live.c2.parent_id
         rows: 1
        Extra: 
*************************** 7. row ***************************
           id: 1
  select_type: SIMPLE
        table: c
         type: eq_ref
possible_keys: PRIMARY
          key: PRIMARY
      key_len: 4
          ref: yozoa1_live.s.parent_id
         rows: 1
        Extra: 


Show create table -     
CREATE TABLE `categoryMaster` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  `description` text NOT NULL,
  `logo` varchar(255) NOT NULL,
  `is_visible` tinyint(1) NOT NULL DEFAULT '1',
  `is_featured` tinyint(1) NOT NULL DEFAULT '0',
  `is_map` tinyint(1) NOT NULL DEFAULT '0',
  `is_price_required` tinyint(1) NOT NULL DEFAULT '1',
  `parent_id` int(11) NOT NULL DEFAULT '0',
  `lft` int(11) NOT NULL DEFAULT '0',
  `rgt` int(11) NOT NULL DEFAULT '0',
  `level` tinyint(4) NOT NULL DEFAULT '0',
  `sort_order` smallint(6) NOT NULL DEFAULT '0',
  `product_count` int(11) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `lft_rgt_inx` (`lft`,`rgt`),
  KEY `parent_id` (`parent_id`),
  KEY `product_count` (`product_count`)
) ENGINE=MyISAM


CREATE TABLE `productMaster` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  `description` longtext NOT NULL,
  `sub_name` varchar(255) NOT NULL,
  `sub_description` longtext NOT NULL,
  `image` varchar(255) NOT NULL,
  `category_id` int(11) NOT NULL,
  `is_new` tinyint(1) NOT NULL DEFAULT '1',
  `status` tinyint(1) NOT NULL DEFAULT '-1',
  `user_id` int(11) NOT NULL,
  `currency_main` varchar(4) NOT NULL DEFAULT 'MNT',
  `price_original` double NOT NULL DEFAULT '0',
  `price_global` double NOT NULL DEFAULT '0',
  `attribute_value_ids` text,
  `created_at` datetime DEFAULT NULL,
  `updated_at` datetime DEFAULT NULL,
  `confirmed_at` datetime DEFAULT NULL,
  `duration` int(4) NOT NULL DEFAULT '7',
  `rental_duration` varchar(50) DEFAULT NULL,
  `buy_online` tinyint(1) NOT NULL DEFAULT '0',
  `internal` tinyint(1) NOT NULL DEFAULT '0',
  `delivery_status` smallint(1) NOT NULL DEFAULT '1'
  `delivery_type` smallint(1) NOT NULL DEFAULT '1'
  `phone_cell` varchar(50) DEFAULT NULL,
  `phone_home` varchar(50) DEFAULT NULL,
  `surname` varchar(100) DEFAULT NULL,
  `x_area_id` int(11) NOT NULL,
  `x_area_location_id` int(11) DEFAULT NULL,
  `sublocality_id` int(11) DEFAULT NULL,
  `product_posting_price` double NOT NULL,
  `is_paid` tinyint(1) NOT NULL,
  `product_posting_currency` varchar(3) NOT NULL,
  `map_lat` double NOT NULL,
  `map_lng` double NOT NULL,
  `product_company_contact_info_id` int(11) NOT NULL,
  `backup_status` tinyint(1) NOT NULL DEFAULT '4',
  `is_scraped` tinyint(1) DEFAULT NULL,
  `sources_id` int(3) NOT NULL,
  `product_source_url` varchar(255) NOT NULL,
  `country_id` int(4) NOT NULL,
  `state_id` int(5) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `UNQ_cmp_icsu` (`id`,`category_id`,`status`,`user_id`),
  KEY `country_id` (`country_id`),
  KEY `state_id` (`state_id`),
  KEY `INX_cmp_sx` (`status`,`x_area_id`),
  KEY `status` (`status`),
  FULLTEXT KEY `name` (`name`),
  FULLTEXT KEY `attribute_value_ids` (`attribute_value_ids`)
) ENGINE=MyISAM


CREATE TABLE `cityMaster` (
  `id` int(10) NOT NULL AUTO_INCREMENT,
  `parent_id` int(6) NOT NULL,
  `name` varchar(255) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
  `map_lat` double NOT NULL,
  `map_lng` double NOT NULL,
  `has_sublocality` tinyint(1) NOT NULL DEFAULT '0',
  PRIMARY KEY (`id`),
  KEY `parent_id` (`parent_id`)
) ENGINE=MyISAM


CREATE TABLE `stateMaster` (
  `id` int(6) NOT NULL AUTO_INCREMENT,
  `parent_id` int(3) NOT NULL,
  `name` varchar(255) NOT NULL,
  `map_lat` double NOT NULL,
  `map_lng` double NOT NULL,
  PRIMARY KEY (`id`),
  KEY `parent_id` (`parent_id`)
) ENGINE=MyISAM


CREATE TABLE `countryMaster` (
  `id` int(3) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  `country_code` varchar(2) CHARACTER SET latin1 NOT NULL,
  `map_lat` double NOT NULL,
  `map_lng` double NOT NULL,
  `is_active` tinyint(1) NOT NULL DEFAULT '1',
  PRIMARY KEY (`id`)
) ENGINE=MyISAM

请建议我如何通过索引减少此查询的执行时间。还让我知道为什么查询说明在ref列中显示null？还让我知道优化查询的步骤吗？