CREATE TABLE `c` (
  `cid` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `qid` int(10) unsigned NOT NULL DEFAULT '0',
  `aid` int(10) NOT NULL DEFAULT '0',
  `URN` int(10) NOT NULL DEFAULT '0',
  `in_id` int(10) unsigned NOT NULL DEFAULT '0',
  `out_id` int(10) unsigned NOT NULL DEFAULT '0',
  `DDIstr` varchar(24) NOT NULL,
  `CLIstr` varchar(24) NOT NULL,
  `datetime` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',
  `microtime` varchar(30) NOT NULL DEFAULT '0 0',
  `duration` float NOT NULL DEFAULT '0',
  `wtime` float NOT NULL DEFAULT '0',
  `wrtime` float NOT NULL DEFAULT '0',
  `rtime` float NOT NULL DEFAULT '0',
  `result` varchar(15) DEFAULT NULL,
  `t_cdr` int(10) DEFAULT NULL,
  `c_outcome` int(10) DEFAULT NULL,
  `d_code` varchar(10) DEFAULT NULL,
  `r_cost` float DEFAULT NULL,
  `c_cost` float DEFAULT NULL,
  `dataset` mediumint(8) NOT NULL DEFAULT '0',
  PRIMARY KEY (`cid`),
  KEY `aid` (`aid`),
  KEY `datetime` (`datetime`),
  KEY `result` (`result`),
  KEY `in_id` (`in_id`),
  KEY `out_id` (`out_id`),
  KEY `c_outcome` (`c_outcome`),
  KEY `qid` (`qid`),
  KEY `d_code` (`d_code`),
  KEY `agentid_2` (`aid`,`datetime`),
  KEY `get_max_cid` (`aid`,`cid`),
  KEY `max_cid_2` (`aid`,`result`,`cid`),
  KEY `t_cdr` (`t_cdr`),
  KEY `c_uid` (`URN`,`qid`),
  KEY `DDISTR_2` (`DDISTR`,`datetime`),
  KEY `CLISTR` (`CLISTR`),
  KEY `qid_2` (`qid`,`datetime`)
) ENGINE=InnoDB 

EXPLAIN
SELECT
   c.`cid` AS `cid`
FROM c
WHERE
   c.result IN ('Answered','TPT') AND
   c.`datetime` BETWEEN '2014-05-01 00:00:00' AND '2014-05-29 23:59:59'
   AND c.qid = 42685
ORDER BY cid LIMIT 300;