MySQL和检查约束 [英] MySQL and Check Constraints

问题描述

我继承了一个使用MySQL并且由PHP前端使用的应用程序。写这个系统的人已经去了一些相当复杂的长度，以确保用户输入的代码是有效的 - 和tat意味着这些代码也存在于另一个表中。

I have inherited an application that uses MySQL and that is used by a PHP front end. The guy that wrote this system has gone to some fairly convoluted lengths to ensure that codes that users enter are valid - and tat means that these codes also exist in another table.

当我第一次看到这里，我想知道为什么他没有使用CHECK约束，让dbms排序 - 我有一个负载的不同的程序实现相同的检查，而不是只有一个地方dbms。然后我发现MySQL不支持Check约束（不严格真实 - 它支持语法，但只是忽略它）。

When I first saw this I wondered why he hadn't used CHECK constraints and let the dbms sort this out - I have visions of a load of different programs implementing the same checks instead of just the one place in the dbms. And then I found out that MySQL doesn't support Check constraints (not strictly true - it supports the syntax but just ignores it).

有一种方法，我可以在MySQL中实现检查约束？

Is there a way that I can implement Check Constraints in MySQL?

任何提示，建议等都是很好的。

Any hints, suggestions etc, would be great.

推荐答案

你可以用触发器实现类似的东西，但MySQL本身不支持CHECK约束。不要担心，它会让你定义它们，只是默默地忽略他们！

You can implement something similar to them with triggers, but MySQL itself doesn't support CHECK constraints. Don't worry though, it'll let you define them and just silently ignore them!

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