Я имею дело с большой проблемой MySQL.Посмотрите на эти запросы.
CREATE TABLE `Users_Coupons_Views` (
`id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
`user_id` bigint(20) NOT NULL,
`coupon_id` bigint(20) unsigned NOT NULL,
`pos` int(10) unsigned DEFAULT NULL,
`insert_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
PRIMARY KEY (`id`),
KEY `idx_cid` (`user_id`,`coupon_id`),
KEY `idx_coupon_id` (`coupon_id`)
) ENGINE=MyISAM AUTO_INCREMENT=35423 DEFAULT CHARSET=utf8
CREATE TABLE `Track_Clicks_Processed` (
`id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
`track_id` bigint(20) unsigned NOT NULL,
`user_id` bigint(20) unsigned NOT NULL,
`ip` bigint(16) unsigned DEFAULT NULL,
`coupon_id` bigint(20) unsigned NOT NULL DEFAULT '0',
`merchant_id` int(11) NOT NULL DEFAULT '-1',
`pos` int(11) NOT NULL DEFAULT '-1',
`city` varchar(32) NOT NULL,
`src` varchar(32) NOT NULL,
`medium` varchar(32) NOT NULL,
`kw` varchar(32) NOT NULL,
`ref` varchar(255) NOT NULL,
`user_agent` varchar(512) NOT NULL,
`insert_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
`ingr` tinyint(1) NOT NULL DEFAULT '0',
`lang` char(2) NOT NULL DEFAULT 'it',
PRIMARY KEY (`id`),
KEY `idx_user_id` (`user_id`),
KEY `idx_coupon_id` (`coupon_id`),
KEY `idx_insert_time` (`insert_time`),
KEY `idx_track_id` (`track_id`),
KEY `idx_A1` (`track_id`),
KEY `idx_cid` (`track_id`,`coupon_id`)
) ENGINE=MyISAM AUTO_INCREMENT=2997731 DEFAULT CHARSET=utf8
Запрос:
EXPLAIN SELECT V.coupon_id, V.user_id, V.insert_time
FROM Track_Clicks_Processed AS C
JOIN Users_Coupons_Views AS V ON ( C.coupon_id = V.coupon_id
AND C.track_id = V.user_id )
Вот результат:
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE V ALL idx_cid,idx_coupon_id NULL NULL NULL 17711
1 SIMPLE C ref idx_coupon_id,idx_track_id,idx_A1,idx_cid idx_cid 16 yoodeal.V.user_id,yoodeal.V.coupon_id 2 Using where; Using index
Он не использует индекс для первой таблицы!Почему?