如何在MySQL中执行复合唯一性？ [英] How can I enforce compound uniqueness in MySQL?

问题描述

我遇到了一个情况，我想确保表的复合元素是唯一的。例如：

I have run into a situation where I want to ensure that a compound element of a table is unique. For example:

Table (
  id char(36) primary key,
  fieldA varChar(12) not null,
  fieldB varChar(36) not null
)

不要将fieldA和fieldB作为复合主键，因为它们经常更改，'id'用作整个系统的参考。

I don't want fieldA and fieldB to be a compound primary key, since they change frequently, and 'id' is used as a reference throughout the system.

fieldA和fieldB是它们本身并不独特，但它们的组合需要独特。因此，例如{{1，Matt，Jones} {2，David，Jones} {3，Matt，Smith}}将是有效数据，但{{1，Matt，Jones}，{2，Matt，Jones }}不会。

fieldA and fieldB are not unique in and of themselves, but their combinations need to be unique. So for example, {{1, Matt, Jones}, {2, David, Jones}, {3, Matt, Smith}} would be valid data, but {{1, Matt, Jones}, {2, Matt, Jones}} would not be.

推荐答案

在表格定义中添加一个UNIQUE键：

Add a UNIQUE key to your table definition:

Table (
  id char(36) primary key,
  fieldA varChar(12) not null,
  fieldB varChar(36) not null,
  UNIQUE fieldA_fieldB (fieldA, fieldB)
)

这篇关于如何在MySQL中执行复合唯一性？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！