This dictionary contains over 1,700 entries dealing with issues, terms, and concepts involved in, or arising from use of, the relational model of data. Most of the entries include not only a definition as such—often several definitions, in fact—but also an illustrative example (sometimes more than one). What’s more, I’ve tried to make those entries as clear, precise, and accurate as I can; they’re based on my own best understanding of the material, an understanding I’ve gradually been honing over some 45 years of involvement in this field.

I’d also like to stress the fact that the dictionary is, as advertised, relational. To that end, I’ve deliberately omitted many topics that are only tangentially connected to relational databases as such (in particular, topics that have to do with database technology in general, as opposed to relational databases specifically); for example, I have little or nothing to say about security, recovery, or concurrency matters. I’ve also omitted certain SQL topics that—despite the fact that SQL is supposed to be a relational language—aren’t really relational at all (cursors, outer join, and SQL’s various “retain duplicates” options are examples here). At the same time, I’ve deliberately included a few nonrelational topics in order to make it clear that, contrary to popular opinion, the topics in question are indeed nonrelational (index is a case in point here).

I must explain too that this is a dictionary with an attitude. It’s my very ...

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