再发两个SQL语句效率，附执行时间图解决办法 | Dami

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再发两个SQL语句效率，附执行时间图解决办法

再发两个SQL语句效率，附执行时间图
select id,title from info where cityid=11 order by id desc

select id,title from info where substring(city,1,2)='11' order by id desc

其中cityID为INT数据类型 city为varchar数据类型

已经发过一个帖子，大家都认为第一个快，我也这么认为，可是我把city和CITYID都建索引后大家自己看结果吧

结果是差不多，甚至第二个稍快
我想问的是为什么会这样请懂得索引的高手支招？

.net 程序开发 asp

12 years, 5 months ago

仅仅如此

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仅仅如此 12 years, 5 months ago

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先关注一下

answered 12 years, 5 months ago

rgw87

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rgw87 answered 12 years, 5 months ago

0

收藏先

answered 12 years, 5 months ago

Skyrail

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Skyrail answered 12 years, 5 months ago

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mark

answered 12 years, 5 months ago

杂念，完蛋去吧

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杂念，完蛋去吧 answered 12 years, 5 months ago

0

不懂。。关注下。。

answered 12 years, 5 months ago

比黑更黑更黑

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比黑更黑更黑 answered 12 years, 5 months ago

0

踩踩

answered 12 years, 5 months ago

傲世苍宇刀无极

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傲世苍宇刀无极 answered 12 years, 5 months ago

0

Mark!

answered 12 years, 5 months ago

旧日支配者

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旧日支配者 answered 12 years, 5 months ago

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没搞过测试,不过数据量小的时候,测试结果很难说准!

answered 12 years, 5 months ago

吹走的帽子君

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吹走的帽子君 answered 12 years, 5 months ago

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是不是测试的有问题，数据量大的时候，第二个明显就慢！

answered 12 years, 5 months ago

卡明特

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卡明特 answered 12 years, 5 months ago

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同意樓上的說法﹐一個 field 盡管有建立index,但該field在where 中套用了函數﹐index就無效

answered 12 years, 5 months ago

6189906

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6189906 answered 12 years, 5 months ago

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MARK

answered 12 years, 5 months ago

death逆刃

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death逆刃 answered 12 years, 5 months ago

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改天看

answered 12 years, 5 months ago

害怕寂寞的魔王

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害怕寂寞的魔王 answered 12 years, 5 months ago

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几乎确定？从语句上看，如果索引键的ok
第一个百分百的快，第二个有没有索引都没用

answered 12 years, 5 months ago

六氯环己烷

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六氯环己烷 answered 12 years, 5 months ago

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测试不懂，学习

answered 12 years, 5 months ago

bondson

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bondson answered 12 years, 5 months ago

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