1. A computer system configured as a database designer for specifying a layout, among a plurality of storage nodes, of a database whose logical design includes at least one table of which each is organized in rows and columns, the computer system being so configured as to: A) determine a physical design for the database by: i) choosing a set of candidate sort orders; and ii) in each of a plurality of projection-selection operations: a) selecting a candidate sort order, from among the candidate sort orders not previously selected, in accordance with the cost of executing training queries on physical projections that have those candidate sort orders; b) identifying the training queries for which addition of a projection having the selected sort order results in a cost-of-execution change that meets some cost-improvement criterion; c) adding to at least one of the storage nodes of the physical design a first physical projection, thereby associated with that projection-selection operation and not similarly associated with a previous projection-selection operation, having the selected sort order and including vertically arranged versions of the logical columns that the training queries thus identified require; and d) adding at least to one different one of the storage nodes of the physical design at least a further physical projection, whose sort order differs from that of the first physical projection, whose physical column versions are versions of the logical columns of which the first physical projection's physical column versions are versions, such that all data in the first physical projection is replicated on more than one of the storage node; and B) generating an output indicative of the resultant physical design.