性能 - 单连接选择与多个简单选择 [英] performance - single join select vs. multiple simple selects

问题描述

解决方案

只有一种方法可以知道： p>

一般来说，我认为单个连接使数据库可以做很多优化，因为它可以看到需要扫描的所有表，开销减少，它可以

最近，我有大约100个选择语句，我在我的代码中改为JOIN。使用几个索引，我可以从1分钟运行时间到大约0.6秒。

What is better as far as performance goes?

解决方案

There is only one way to know: Time it.

In general, I think a single join enables the database to do a lot of optimizations, as it can see all the tables it needs to scan, overhead is reduced, and it can build up the result set locally.

Recently, I had about 100 select-statements which I changed into a JOIN in my code. With a few indexes, I was able to go from 1 minute running time to about 0.6 seconds.

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