Service Oriented Architecture and Loose Coupling vs SQL JOINS

Suppose we have an SOA infrastructure similar to the one written below, and that each service can run on a different host (this is especially true for two additional network services, “website” and “payment system”).

It is clear that we have a data layer (persistence). Suppose it is implemented through EJB + JPA or something similar.

If we want to combine data (in the user interface) between different services, I see at least a couple of alternatives:

• JOIN , ( persistence.package), ( CRUD), - (? ) . , - , , . , .

• , ( order.package) (, , esb ..). ( ), . , , , ( SQL-)

/ , ?