Each can do the other, to a limited extent, but it becomes increasingly difficult with even small increases in complexity. For instance, you can do inferencing in SQL, but it is almost entirely manual in nature and not at all like the automatic forward-inferencing of Prolog. And yes, you can store data(facts) in Prolog, but it is not at all designed for the "storage, retrieval, projection and reduction of Trillions of rows with thousands of simultaneous users" that SQL is.
I even wanted to implement something like Logica at the moment, primarily trying to build a bridge through a virtual table in SQLite that would allow storing rules as mostly Prolog statements and having adapters to SQL storage when inference needs facts.