如何为组合主键创建外参考键 [英] how to create foreign reference key for composition primary key

问题描述

假设我们有以下两个表

Create table Bank (
   Bank_ID Numeric Not Null,
   Bank_Card Numeric Not Null,
   Primary Key(Bank_ID, Bank_Card)
)

Create table Customer (
   Customer_ID Numeric Not Null,
   Name varchar(30) Not Null,
   Primary key(Customer_ID)
)

其中通过合并Bank_ID和Bank_Card生成Customer_ID的位置.如何设置外键Customer_ID以引用Bank_ID和Bank_Card

Where Customer_ID is generated by concatenating Bank_ID and Bank_Card. How can I set foreign key Customer_ID to reference Bank_ID and Bank_Card

推荐答案

所需的是约束，但它不是FK(外键)约束.(FK约束表示列列表的值在其他地方显示为PK /UNIQUE.)要声明性地执行它，可以在Bank中添加冗余的生成(计算/计算)列Customer_ID，并在Customer中添加FK.要执行它而不添加多余的列，您需要触发器.但是智能密钥是个坏主意.

What you want is a constraint, but it's not a FK (foreign key) constraint.(A FK constraint says that values for a column list appear elsewhere as PK/UNIQUE.) To enforce it declaratively you could add redundant generated (computed/calculated) column Customer_ID to Bank and a FK to it in Customer. To enforce it without adding redundant columns you need triggers. But smart keys are a bad idea.

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