The Theory of Relational Databases (1983)

http://web.cecs.pdx.edu/~maier/TheoryBook/TRD.html

by dragontamer • 7 years ago

261 24 7 years ago

web.cecs.pdx.edu

Maier's The Theory of Relational Databases is one of the most highly cited textbooks on Relational Theory. I've given the first 2 chapters a look over, and I can see why: the writing style is clear, and its concepts are so fundamental that they are still applicable today (roughly 36 years after this textbook was first published).

I haven't read all of this yet, but I figure someone out there will find it helpful. My personal use of this textbook is for constraint-programming, which is closely related to the Relational Theory used in relational databases.

lqet• 7 years ago

I also read the beginning of a few chapters and have to agree: the writing style is very concise.

Example (from the Introduction):

  One of the major advantages of the relational model is its uniformity. All data
  is viewed as being stored in tables, with each row in the table having the same
  format. Each row in the table summarizes some object or relationship in the
  real world. Whether the corresponding entities in the real world actually
  possess the uniformity the relational model ascribes to them is a question
  that the user of the model must answer. It is a question of the suitability of
  the model for the application at hand.
  Whether or not the relational model is appropriate for a particular set of
  data shall not concern us. There are plenty of instances where the model is
  appropriate, and we always assume we are dealing with such instances.

talaketu3• 7 years ago

Worth noting that here the use of the word "model" refers not to some indefinite domain-specific data schema, but "The Relational Model" as a paradigm.

It displaced the earlier paradigm of hierarchical data model, which derived more or less from physical media (eg punch cards).

The relational model is not well suited to uncertain data, as a row in a table is generally interpreted as a true proposition. For statistical data sets, analytical processing may be better served by array/tensor models (which also exhibit uniformity).

tjpnz• 7 years ago

http://web.cecs.pdx.edu/~maier/TheoryBook/TRD.html

jonahx• 7 years ago

Anyone know the significance of the diagrams on the book's cover? They're intriguing:

https://i.imgur.com/24LEJyf.png

Scarbutt2• 7 years ago

Set theory.

dragontamer5• 7 years ago

I'm going to guess that the pictures are of hypergraphs. Hypergraphs are good representations of mathematical relations. Each vertex of the hypergraph is a domain, while a hyperedge would be a "relation", the subject of the book.

https://en.wikipedia.org/wiki/Hypergraph

For those unfamiliar with hypergraphs, they are very similar to classical graphs. Except hyperedges may connect more than two vertices together. (While normal graph edges normally only connect two vertices together) Therefore, you have to draw regions to represent hyperedges.

joshypants• 7 years ago

Does anyone know what the hyper- prefix here signifies? These diagrams remind me of microphone response graphs, and there's a type of microphone called hypercardioid that resembles this shape.

david-maier3• 7 years ago

The diagrams are indeed hypergraphs. They are taken from Chapter 12 of the book, and are simplifications of Figures 12.44 and 12.45. The solid lines enclose relation schemes, and the dotted line represent "objects", which here signify groups of relations it makes sense to join. There's a scan of the text at http://web.cecs.pdx.edu/~maier/TheoryBook/TRD.html if you want to look at the figure originals.

dragontamer5• 7 years ago

Good eye! They look precisely like figure 12.44 and 12.45!

jesuslop• 7 years ago

Gallo et al. expressed functional dependencies via them here https://www.sciencedirect.com/science/article/pii/0166218X93...

ww520• 7 years ago

Relational model is basically Set. The diagram is illustrating the sets.

OldSQLDude• 7 years ago

I started my IT career in the late '80s...and the buzz of the day was SQL. All the money those days (consulting, I mean) was for dBase. But the limits were becoming obvious (scale, mostly) and relational db's were moving rapidly. Yep, when Oracle was just an RDBMS. To learn SQL... well, hit the library. Lots of boring stuff on "relational calculus", but nothing I perceived as valuable. I found Maier's book...and while it had a lot of math, there was enough practical content that the lights came on for me. After that, I found books from E.F. Codd and Chris Date...wonderful! If you want to nerd out on this stuff, find the more recent works by Chris Date. I recall having many beers over null. And wacky joins. I haven't had to write SQL for pay in years...but for me, SQL and RDBMS are a wonderful diversion on the occasion I'm asked to unravel an issue. For some reason, the relational model still makes sense to me...and I don't know if it is because it's the first formal model I worked with, or of it's intrinsic value. Perhaps you never forget your first love. Anyhow, my advice to people digging into this, is to install (or get access to) a reasonably complete RDBMS, and create/populate a few tables and attempt to predict what your SQL will return. This is a key skill. I see so many devs writing queries and testing them... and watching what comes back and then (somehow) thinking they've got it right. Sure, with a few dozen rows...but try that on several million records. Nope. At scale, you must understand the relational model in general, AND you must profile the RDBMS you are running by experimentation to see exactly how it behaves... especially around nulls, default sort orders, and joins. Not all RDBMS behave the same way... and this will surprise most.

mastrsushi• 7 years ago

Does anyone know if they offer this as a full pdf? I have no idea why they decided to split it. I'm sure it's not hard to merge back.

david-maier3• 7 years ago

Why is the book in parts? It was scanned almost 20 years ago, when multi-megabyte files were still challenging for some tools to deal with. I'm guessing as a single file, it would be 50+ MB.

(Note that the book was written before PDF existed.)

The Theory of Relational Databases (1983)

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