source: https://msdn.microsoft.com/en-us/library/ms188251.aspx

Examples above

I understand one to one relationships, one to many, PK, FK and all of that, but

I get really confused about understanding what verical lines refer in a relational database setup

Could someone elaborate on the highlighted area?

What is #1 and #2 referring to in this diagram?

Is #1 referring to a one to many relationship for COUNTRY: TITLEID? and #2 discount to STORE ID?

I'm having trouble visually interpreting the diagram

1 Answer 1


The answer for to your question is further down in the article:

Endpoints The endpoints of the line indicate whether the relationship is one-to-one or one-to-many. If a relationship has a key at one endpoint and a figure-eight at the other, it is a one-to-many relationship. If a relationship has a key at each endpoint, it is a one-to-one relationship.

The key represents the "one" and the figure-eight (or infinity symbol, I presume) represents the "many".

The relationships aren't tied to the visually closest column name in the diagram, but to the column with the same name in each table. For instance, the one-to-many relationship between publishers and titles is tied to the pub_id column.

  • If I'm not mistaken in MSaccess, the columns don't have to be the same name, and are enforced visually per column. In MS SQL server and other RDBMS, columns between two tables have to be named the same? Commented Nov 22, 2016 at 21:31
  • is it also assumed in this case, discounts.Store_ID is a foreign key? Commented Nov 22, 2016 at 21:32
  • The columns that define the relationships between the tables in this specific example just happen to have the same name, but that isn't a requirement for SQL Server or other RDBMs. As the DBA, you are responsible for defining the relationships. And yes, discounts.stor_id would be the foreign key in the relationship between the stores and discounts tables. Commented Nov 23, 2016 at 13:16

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