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CREATE TABLE `ch1` (
  `id` int(10) unsigned zerofill NOT NULL AUTO_INCREMENT,
  `no` int(10) unsigned DEFAULT NULL,
  `dtime` datetime DEFAULT NULL,
  PRIMARY KEY (`id`)
)
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create index idx_dtime on ch1(dtime);

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CREATE TABLE `ch1` (
  `id` int(10) unsigned zerofill NOT NULL AUTO_INCREMENT,
  `no` int(10) unsigned DEFAULT NULL,
  `dtime` datetime DEFAULT NULL,
  PRIMARY KEY (`id`)
)
²éѯÓï¾ä select sum(no) as number,dtime as date from ch1 group by month(dtime)
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  Extra£º Using temporary; Using filesort

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create index idx_dtime on ch1(dtime);

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  Extra£º Using temporary; Using filesort

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select sum(