https://docs.intersystems.com/irislatest/csp/docbook/DocBook.UI.Page.cls?KEY=GSQL_IMPLICITJOINS https://docs.intersystems.com/irislatest/csp/docbook/DocBook...

https://docs.intersystems.com/irislatest/csp/docbook/DocBook.UI.Page.cls?KEY=GSQL_IMPLICITJOINS https://docs.intersystems.com/irislatest/csp/docbook/DocBook... -> is really just syntactic sugar for a left outer join, which implicitly becomes an inner join if a foreign key constraint is present. How it ends up resolved is up to the optimizer, whether there's a foreign key available it might exploit or not.