Hi Richard! I am trying to get my head around this again. lol.

Relationship Seminar, Lesson 15, at 6:22 you said you have members which is a many to many relationship. I take this to mean that multiple members can belong to multiple organizations.  Right?

Then you said that addresses is a one to many relationship, from either an organization or a member.  This is where I am confused.  A member can have multiple addresses, and an org can have multiple addresses. But the address is only listed in the table once. And the address can only be used by either the member "OR" the organization. Is this right? Do I finally get it?

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Reply from Alex Hedley:

Maybe this MS article with the following example may help:

One-to-many relationships

A one-to-many relationship is the most common kind of relationship. In this kind of relationship, a row in table A can have many matching rows in table B. But a row in table B can have only one matching row in table A. For example, the "Publishers" and "Titles" tables have a one-to-many relationship. That is, each publisher produces many titles. But each title comes from only one publisher.

Many-to-many relationships

In a many-to-many relationship, a row in table A can have many matching rows in table B, and vice versa. You create such a relationship by defining a third table that is called a junction table. The primary key of the junction table consists of the foreign keys from both table A and table B. For example, the "Authors" table and the "Titles" table have a many-to-many relationship that is defined by a one-to-many relationship from each of these tables to the "TitleAuthors" table.