Many to many relationship classes

04-29-2021 08:33 AM
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New Contributor III

HI have worked with relationship classes before but almost entirely in a 1:1 system. I am currently trying to work out how to build a relationship class where the records aren't quite as convenient; I'll describe the real life situation.

I have a point layer of schools, and a polygon layer of catchments for each school. There are situations where one catchment could relates to 2 or more schools (depending on the capacity each year), so then in turn those schools are related to at least two catchments (ie its own catchment and the shared catchment).

Normally I'd just assign a field with an ID which matches in both tables, however there will be multiple matches in both tables. How do I manage this in the M:N set up?

I am using ArcGIS Pro but also have access to ArcMap and Portal



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MVP Esteemed Contributor

Just checking if you have looked at this article.

How To: Create a many-to-many relationship in a geodatabase 

In one-to-one and one-to-many relationships, values in the primary key of the origin class directly relate to values in the foreign key of the destination class.

Many-to-many relationships, on the other hand, require the use of an intermediate table to map the associations. As a result, when you create a many-to-many relationship, an intermediate table is automatically created. The intermediate table maps primary key values from the origin to foreign key values from the destination. Each row associates one origin object with one destination object.



Many-to-many relationships 

Think Location