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select-mysql查询count值查不出来，显示查询超时

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Release： 2016-06-06 09:43:13
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mysqlselect超时count

SELECT count(test.exam.id)
FROM test.exam
left join test.user
on test.exam.sfz=test.user.sfz
where test.user.area=13
查询不出来总数，最后会显示超时
每个表都有20万条左右数据

会查询600秒

Related labels：
mysql select 超时 count
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