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奇怪的问题,但为什么我们称它为innervs. outer join?术语join,left和right对我来说很有意义,但inner并不outer那么明显。
inner
outer join
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每个查询背后都有关系代数。维恩图提供了对此的快速直观理解。检查此维基百科链接
...哎呀...关闭
在底层 SQL 是一个关系代数引擎,看看http://en.wikipedia.org/wiki/Relational_algebra