选择花20秒？如果我删除订单只需要0,020

Question

我有这个选择：

select c.user, p.user, p.title, cm.user, cm.block, pp.foto from members cm
left join topics p on cm.member = p.id
left join profile_picture pp on pp.user = cm.user
left join cadastro c on cm.user = c.id
where cm.member = 1 and ((p.user = 10) or ((p.user != 10) and (cm.block = 0)))
group by cm.user
order by cm.block desc, cm.data desc
limit 0,100

无订单解释：

按顺序解释：

`members` (
  `id` int(11) UNSIGNED NOT NULL AUTO_INCREMENT,
  `user` INT(11) UNSIGNED NOT NULL,
  `member` INT(11) UNSIGNED NOT NULL,
  `data` datetime NOT NULL,
  `ip` varchar(20),
  `block` tinyint(1) NOT NULL DEFAULT '0',
  UNIQUE KEY (`user`, `member`),
  PRIMARY KEY (`id`),
  KEY `member_block` ( `member`, `block`),
  FOREIGN KEY (`user`) REFERENCES cadastro (`id`),
  FOREIGN KEY (`member`) REFERENCES topics (`id`)
)

and topics

`topics` (
  `id` int(11) UNSIGNED NOT NULL AUTO_INCREMENT,
  `user` INT(11) UNSIGNED NOT NULL,
  `title` varchar(40),
  `description` varchar(500) NOT NULL,
  `foto` varchar(400),
  `data` datetime NOT NULL,
  `ip` varchar(20),
  `privado` tinyint(1) NOT NULL DEFAULT '0',
  `delete` tinyint(1) NOT NULL DEFAULT '0',
  PRIMARY KEY (`id`),
  FOREIGN KEY (`user`) REFERENCES cadastro (`id`)
)

我在cm.block和cm.data上尝试了一个索引，但没有成功。任何想法？