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表连接与外键连接有什么区别？

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Release： 2016-06-06 20:42:19
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表连接与外键连接有什么区别？

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表连接与外键连接有什么区别？

表连接是table join的query，执行sql的时候

外键是表间的存在的关系

表连接是多表查询时候,不同的表里有关系字段的连接,是你通过sql来控制的
外键是一种约束,是dbms管理的,如果一个表里的一个字段的外键是另一个表里的字段值,那么dbms会检查合法性

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mysql php web Database Design
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