A Remark on Terminology


In that list of relational issues in the foregoing section, you probably noticed right away that I used the formal terms relation, tuple,[*] and attribute. SQL doesn't use these terms, of course it uses the more "user-friendly" terms table, row, and column instead. And I'm generally sympathetic to the idea of more user-friendly terms if they can help make the ideas more palatable. In the case at hand, however, it seems to me that, regrettably, they don't make the ideas more palatable; instead, they distort them, and in fact do the cause of genuine understanding a grave disservice. The truth is, a relation is not a table, a tuple is not a row, and an attribute is not a column. And while it might be acceptable to pretend otherwise in informal contexts indeed, I've done so myself, in many of my books and other writings I would argue that it's acceptable only if we all understand that the more user-friendly terms are just an approximation to the truth and fail overall to capture the essence of what's really going on. To put it another way: if you do understand the true state of affairs, then judicious use of the user-friendly terms can be a good idea; but in order to learn and appreciate that true state of affairs in the first place, you really do need to come to grips with the more formal terms. In this book, therefore, I'll use those more formal terms most of the time and of course I'll give precise definitions for them when we need them (mostly not in this first chapter, though, where I'm just trying to lay a certain amount of elementary groundwork).

[*] Usually pronounced to rhyme with couple.

And another point on terminology: having said that SQL tries to simplify one set of terms, I must now add that it does its best to complicate another. I refer to its use of the terms operator, function, procedure, routine, and method, all of which refer to essentially the same thing (with, perhaps, very minor differences). In this book I'll use the term operator throughout.

Talking of SQL, by the way, please note that I use the term SQL to mean the standard version of that language exclusively, not some product-specific dialect barring explicit statements to the contrary, of course. (I did mention this point in the preface, but I know that few people actually read prefaces.) In particular, my criticisms of SQL apply to the standard version specifically. Thus, if some particular criticism happens not to apply to your own favorite product, well, good, I'm glad to hear it (and bully for you).



Database in Depth
Database in Depth: Relational Theory for Practitioners
ISBN: 0596100124
EAN: 2147483647
Year: 2006
Pages: 127
Authors: C.J. Date

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