Relationship between content types I have two content types: Region and City. Region nodes include City nodes; every City node is related to some Region node.

How I can create a relationship for this situation? When I create a Region node and refer a City node in a field, all City nodes have its Region referencing field set to this Region node and vice versa.
You can use Corresponding Entity References to achieve this.

Follow these steps:


Create two content types: Region and City.
Insert entity reference field: Cities in Region and Region in City.
Now enable Corresponding Entity References and update its configuration by going on your site: Configuration >> System >> Corresponding entity references.
Check this configuration: Correspond Region on node(s) of type city with Cities on node(s) of type region.

Now in next tab Updating existing entities of entity type: node.