Q: "My understanding has always been that a primary key should be immutable, and my searching since reading this answer has only provided answers which reflect the same as a best practice. Under what circumstances would a primary key value need to be altered after the record is created?"
A: "When a primary key is chosen that is not immutable?" --StackExchange.com
2. Quote of the Week
"We start with a value. This may be a number, a date, or a chunk of text. Domain refers to the meaning for a value or a set of possible values. When we have a value with a consistently and widely used set of units, value domains, or applications, we call this value a data element. A data element may be a ticket number, a temperature reading, a hair color. (Some modeling approaches omit the notion of data elements or domains.)
In all the techniques and stages of data modeling, the concepts of entity and attribute are universal. An entity is the “thing” that must be manipulated as a data object. Entity represents an indivisible concept that consists of data elements. Each data element in the entity is called an attribute. Conversely, we could say that we build an entity by attributing data elements to it. You create an entity as a whole, and you delete it as a whole." --What a Concept! Is Logical Data Modeling Obsolete? -- LinkedIn.comNote: In the preface to my PRACTICAL DATABASE FOUNDATIONS series of papers I deplored an author's (considered an expert) reliance on an industry ANSI committee as a starting point in an explanation of conceptual, logical and physical data fundamentals--there is practically 0 chance of soundness and 100% chance of confusion. So when this article started with "In the common usage established by ANSI in 1975, data modeling goes from abstract to concrete in three steps" I knew I would not read very far. Sure enough, I stopped almost immediately, after the above quote. If you don't understand why, I recommend you check out my papers.
3. To Laugh or Cry?
4. Added the following to the LINKS page:
- On making Relational Division Comprehensible
- A Relational Model of Data for Large Shared Data Banks
- Dataphor SQL RAC (Relational Application Companion)
5. Of Interest
Note: David McGoveran, who is a OO principles proponents, has long pointed out that OO models (and so the OO programs that implement them) are brittle. If the relationships between classes change, the entire class hierarchy has to be redone. That doesn't mean they don't have value, just that you get the benefits within a particular endeavor. Reusing classes across an enterprise in multiple applications is pretty much limited to what people call "foundation classes" (think of them as utility classes that are so abstract they can be used just about anywhere), not the kind of reuse this fellow was expecting to achieve. OO presumes that everyone will understand a domain of knowledge in exactly one way so that we all agree on what the object classes need to be. It also assumes that classes can be designed in such a way that different classes are independent of each other.
And now for something completely different
The PostWest (The future of the West is all behind it)
- The West fundamentally misunderstands the ethos of the caliphate
- Bush Gave Us Iraq and Afghanistan, Obama Iran
- The Crisis of Political Islam
- Revenge of the Sunnis
Pinch me of the week
Video of the week
Book of the week (Order via link to support this site)
Andersen, C., AMERICAN EVITA: HILLARY CLINTON'S PATH TO POWER
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