If you are naming your foreign key fields consistently for example extras.products_id -> products.id or using some fairly unique data type like GUID for your keys it could be intelligently inferred.

Newbie here. How do you express foreign key - primary key relationships when you define your schema, in Postgresql and/or SQLServer ? Is it via an integrity constraint, or can it be just an informative metadata ?

I’m curious how frequently people actually encounter foreign key constraints in production.

I’m 10 years in and have only ever seen it once