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sql-server - ER图：未连接到任何其他表的表

问题描述

我正在看几年前整理的 ER 图。图中有一个表未连接到任何其他表。

这张桌子有什么用途/它可以用来做什么？

我尝试搜索 Stackoverflow 和 Google，但实际上没有人回答这个问题。

编辑#1：澄清

我的印象是，所有表都必须以某种方式在 ER 图中连接，如果不是，则有问题。

标签： sql-serverentity-relationship-modeler-diagrams

解决方案

I spoke with someone more senior than I am and this is how they explained it to me:

Let's pretend I am building an ER diagram for a restaurant.

I have 3 tables:

  1. Orders
  2. Employees
  3. Inventory

These are all in the same ER diagram. Tables 1 and 2 are connected, but nothing is connected to table 3.

Tables do not all have to be connected in an ER Diagram, but there has to be a purpose for having it there.

If we are creating an ERD to show seating availability, having table 3 would not make any sense as it is not relevant.

If we are designing the whole restaurant set of processes, then you can have stuff that isn't connected as they will obviously be part of their own contained processes.

TLDR: Not all tables have to be connected in an ER diagram, but all tables should relate to the same set of processes.

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