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Chicken Sandwich No Pickles
Chicken Sandwich No Pickles

Reputation: 3362

ER Diagram: Table that is not connected to any other table

I am looking at an ER Diagram put together several years ago. There is a table in the diagram that is not connected to any other table.

What purpose does this table serve / what could it be used for?

I tried searching Stackoverflow and Google, but nobody actually answers this question.

Edit #1: Clarification

I am under the impression that all tables have to be connected in some way in an ER diagram and if they are not, something is wrong.

Upvotes: 0

Views: 4474

Answers (1)

Chicken Sandwich No Pickles
Chicken Sandwich No Pickles

Reputation: 3362

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.

Upvotes: 1

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