Chapter 1 - The Fundamentals Flashcards
What do the first five chapters of the book cover?
They are devoted to the fundamental tasks of relational database design.
What is modeling?
Is the process of capturing the essence of a system in a known language that is common to the user. Is often used as a generic term for the overall process of creating a database.
What is data modeling?
Is a specific type of model that focuses entirely on the storage and management of the data storage medium.
Who was the “founder” of relational database design?
Edgar F. Codd
What year did the “founder” write his first paper?
1979
What was the “founders” original paper called?
“A Relational Model of Data for Large Shared Data Banks”
Who wrote the other two seminal works on relational database design?
Edgar F. Codd. In 1985.
What is the name of the “founders” second work?
“Is Your DBMS Really Relational?”
What is the name of the “founders” third work?
“Does your DBMS Run By the Rules
What is the name of Rule 1?
The Information Principle
What is the formal definition of Rule 1?
All information in the relational database is represented in exactly one and only one way - by values in tables
What is the name of Rule 2?
Guaranteed Access
What is the formal definition of Rule 2?
Each and every datum (atomic value) is guaranteed to be logically accessible by resorting to a combination of table name, primary key value, and column name.
What is the point of Rule 1?
When Codd wrote the rules, there were several different ways that data was being stored. Codd wanted to “abstract” the way the data was presented to the user. So, the user only sees a table with rows and columns but the database engine developer is free to save the data using any underlying format they want.
What is the point of Rule 2?
The rule is about how data is accessed in a table. The primary key will uniquely identify any row in the table. The column will hold a single attribute of that row. It is basically the “addressing system” for the data.
What does “atomic” mean?
It means a value that cannot be broken down any further without losing its fundamental value.
What is the name Rule 3?
Systemic Treatment of NULL Values
What is the formal definition of Rule 3?
NULL values (distinct from empty character string or a string of blank characters and distinct from zero or any other number) are supported in the fully relational RDBMS for representing missing information in a systemic way, independent of data type.
What is the point of Rule 3?
NULL indicates that you don’t have a value to use for a particular attribute. Codd did not want every RDBMS or programmer to come up with their own way to indicating “no data”. NULL means “unknown”. NULL indicates an unknown value of a string and propagates through a math formula. Anything added to “unknown” is still “unknown”.
What is the name of Rule 4?
Dynamic Online Catalog Based on the Relational Model
What is the formal definition of Rule 4?
The database description is represented at the logical level in the same way as ordinary data, so authorized users can apply the same relational language to its interrogation as they apply to regular data.