1. Database Truth of the Week
"If the physical model does not preserve the properties of the logical model, then it is—by definition—incorrect. That is why the physical model must be derived from the logical model, not the other way around." --David McGoveran
2. What's Wrong With This Database Picture?
"If we step back and look at what RDBMS is, we’ll no doubt be able to conclude that, as its name suggests (i.e. Relational Database Management System), it is a system that specializes in managing the data in a relational fashion. Nothing more. Folks, it’s important to keep in mind that it manages the data, not the MEANING of the data! And if you really need a parallel, RDBMS is much more akin to a word processor than to an operating system. A word processor (such as the much maligned MS Word, or a much nicer WordPress, for example) specializes in managing words. It does not specialize in managing the meaning of the words ... So who is then responsible for managing the meaning of the words? It’s the author, who else? Why should we tolerate RDBMS opinions on our data? We’re the masters, RDBMS is the servant, it should shut up and serve. End of discussion." --Alex Bunardzic, Should Database Manage The Meaning?
Here's what's wrong with the picture of two weeks ago, namely:
"Constraints are categorized as follows:
- Domain integrity Constraints
- Entity integrity Constraints
- Referential integrity Constraints
- Not null
- Unique
- Foreign key
- Check
- Primary key
Constraints are always attached to a column not a table."
--Dayakar, SQL Constraints
Despite being a critical database function, integrity is insufficiently understood and appreciated. Few practitioners know much beyond just awareness of primary key and referential constraints and question even their necessity.
SQL inhibits understanding, so if you want to really understand integrity, don't start with SQL. Instead, educate yourself on relational integrity and put your SQL DBMS's features in that context--how correctly and completely does it support all the necessary constraints? Then you can (1) make sure that the constraints that it does support are enforced and (2) be aware of those that it does not, the potential risks thereof and the defensive actions to be taken, if necessary. A bonus is that you will finally realize one of the many important differences between SQL DBMSs and a true RDBMS, which are confused in the industry[1].
I dare you to find this information anywhere else!!!!
"...having nothing in them of the feelings or principles of ’76 now look to a single and splendid government of an Aristocracy, founded on banking institutions and monied incorporations under the guise and cloak of their favored branches of manufactures commerce and navigation [add technology], riding and ruling over the plundered ploughman and beggared yeomanry." --Thomas Jefferson
The first Donald Trump who comes along is all it takes to dismantle 200 years of American vaunted democracy and whatever little civilization was there by executive order. The "indestructible" system of checks and balances is collapsing like a house of cards.
A nation that substitutes job training--if anything--for education, religion for reason and unbounded greed for morality regresses to the dark ages and self destructs.
1. Database Truth of the Week
“… logic—is an analytical theory of the art of reasoning whose goal is to systematize and codify principles of valid reasoning. It has emerged from a study of the use of language in argument and persuasion and it is based on the identification and examination of those parts of language which are essential for these purposes. It is formal in the sense that it lacks reference to meaning. Thereby, it achieves versatility: it may be used to judge the correctness of a chain of reasoning (in particular, a “mathematical proof”) solely on the basis of the form (and not the content) of the sequence of statements, which make up the chain.” --R. R. Stoll
Database Truth of the Week
"... systems of operations on data are most effective when they are formalisms, in which semantic considerations are unimportant until the formalism is applied to some specific application. In this way, database processing can join the ranks of successful mathematical abstractions. Differential equations, for instance, can be applied to situations ranging from orbit calculations to the quantum mechanics of the atom. The semantics of each application is unique to that application, but the formalism of differential equations is common. The power of the formalism lies in its abstraction from issues of meaning." --H. T. Merrett, Extending the Relational Algebra to Capture Less Meaning
