In practice the boundary between both is fuzzy. Processing DB data can and is often done in a row-by-row or cell-by-cell basis. Not all computations are conveni

In practice the boundary between both is fuzzy. Processing DB data can and is often done in a row-by-row or cell-by-cell basis. Not all computations are convenient to reduce to relational algebra, at least for most practitioners. We can't all be Sheldons.