Design Theory of Relational Databases (original) (raw)
69. Where we are. Over the last few weeks we have looked at conceptual design via entity relationship diagrams, and last lecture we discussed how such a diagram can be translated into actual tables. If the conceptual model was sufficiently accurate and adequate, then the resulting tables will constitute a very good starting point for the logical design. It is unlikely, however, that the tables are already in the optimal shape for representing the real-world data. Indeed, it is very common that certain redundancies remain; such redundancies will lead to inefficiencies and are sources of potential errors. As part of the logical design phase, therefore, we should have a close look at each table that results from ER modelling. The single most effective technique for doing so is to check the tables for potential functional dependencies. Once these have been established, the tables can be optimized in a fairly mechanical procedure, called normalisation. This will be the topic of the next ...
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