Deep links allow to reference properties on other documents at request time. But deep links are only available for select clauses and on the right side of where constraints. If you need to take information from the result set into account, there is currently no tool in the projectdoc Toolbox for Confluence to support this use case in queries.

For many use cases this situation could be solved by materializing properties from other documents. Materializing means that there is a property for the document that renders a property from another document. This way there is no longer the need for a deep link on the right side of a where clause.

The tools to accomplish this are Display Document Property Ref Macro, its cousin Display Document Property Ref Concat Macro, and the Parent Property Macro.