The theory of relational databases has much in common with the mathematical structures central to the Z notation. Many authors have noted these connections in the past, but the development of the Z standard has provided a more natural way of making these links explicit. We explore extensions to the schema calculus that may help to model the familiar relational algebra operations in a clear way. Potential areas of application for this work include pedagogy, practical database design, and helping to point the way towards a more general means for defining a broader class of schema calculus operations.