外键引用多个表 [英] Foreign key refering to multiple tables

问题描述

我有4个表

A(ida, name)
B(ida, B-specific stuff)
C(ida, C-specific stuff)
D(ida, D-specific stuff)

，我想要另一个表E可以指B或C（不是D）。我可以在

and i want that another table E could refer to just B OR C (not D). What can i write in the

CREATE TABLE E

？

推荐答案

似乎我想要使用某种超类型/子类型 - 而不是简单的垂直分区。如果是这样，请介绍一个类型鉴别器。

Seems to me that you are trying to use some kind of supertype/subtype -- as opposed to simple vertical partitioning. If so, do introduce a type-discriminator.

因为这是一般的例子（A，B，C，D ..），很难猜出与什么关系，所以这里有两个选择作为我最好的猜测。

Because this is generic example (A, B, C, D ..) it is hard to guess what relates to what, so here are two options as my best guess.

选项1

选项2

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