How to join the tables in database using postgraphile?
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### Summary
I have a cloudquery postgress DB for which we have multiple tables for each resource type.
I want to join these tables to get all details for a single resource. 

For example, I am having 3 different tables like ec2_metadata, ec2_instances, ec2_instance_types. Internally, how to connect all these tables and join them (like join ec2_metadata and ec2_instance_types (or) ec2_instances and ec2_instance_types). 

Also, to join the tables in postgraphile do we actually require foreign key relationship?

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