Some database tables include a relational field, where a record of the table stores a foreign-key reference value that identifies a related record of a second table. While fulfilling a request comprising a query over the database, the system may identify a context of the request, wherein the context is supplemental to the query, and wherein the context relates to the relational field. For example, a security policy may permit a requester to query the first table, but restrict the requester from accessing the second table that the relational field of the first table references, where dereferencing the relational field may cause unexpected results. Instead, the system may evaluate the context of the request, and may fulfill the request based on the context by providing a response that substitutes, for the value that references the second table, a substitute value that does not reference the second table.