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In database discussions, for creating many to many relationship class we must create a third table to relate two other tables.

However, in ArcGIS for creating many to many relationship class we just introduce two tables.

How does ArcGIS create a many to many relationship class without a third table?

forexample we have this issue

"A user can belong to multiple community, and a community can have multiple users"

enter image description here

forexample in "table to relationship class" tool we have three tables

and because ArcGIS does not know which origin objects are associated with which destination objects, so you must manually populate the rows

so we must have third table to link two others

this is the link that describe it

https://desktop.arcgis.com/en/arcmap/10.3/manage-data/relationships/populating-an-attributed-relationship-class-table-.htm

enter image description here

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It doesn't. It does create a 3rd table. ArcGIS creates a wide variety of tables in its databases that it does not expose to the user in the user interface of ArcMap or ArcGIS Pro. The additional table for a relationship class is just one of them.

The documentation for creating a relationship class explicitly states:

For many-to-many relationship classes, a new table is created in the database to store the foreign keys used to link the origin and destination classes.

https://desktop.arcgis.com/en/arcmap/10.3/tools/data-management-toolbox/create-relationship-class.htm

(Other tables it can create in databases that are not directly exposed to the user include versioning add/delete/update tables, archive history tables.)

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  • thanks @Son of a Beach
    – saeedzali
    Nov 27 at 0:29
  • but now I search for it and find a tool names "table to relationship class" that it is exactly that I want.
    – saeedzali
    Nov 27 at 0:31
  • it is exactly the one that I describe it in my question.
    – saeedzali
    Nov 27 at 0:32
  • this sentence is the key:
    – saeedzali
    Nov 27 at 0:35
  • "ArcGIS does not know which origin objects are associated with which destination objects, so you must manually populate the rows"
    – saeedzali
    Nov 27 at 0:35

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