Week 4:Databases

Wikipedia: Databases

I like the idea that databases are like rooms in a hotel. The visual simplifies the larger concept for me.   I think I know understand that a database is a computer application whose purpose is to store information.  It then allows it to be retrieved at will later by many users.  Simple right!  A relational database is more complicated than that.  It allows the information to access through a variety of access paths by means of requests (queries) that return sets of information by reference to common or related properties.  Now –a  day it is the relational database  that we interact with in professional ways.  Databases use SQL (standard query language)- which defines the command language for making a request (the query) to any database.  The typical request is known as CRUD, standing for Create, Read, Update, Delete.  Which are the four primary commands in SQL.

Wikipedia: Entity-Relationship Model:

Entity-relationship model is a graphical representation of how the objects in a relational database management system are related to one another.  My husband has some on his computer right now for work.  It seems to only to be used for planning or documenting the structure of a database.

Phlonx tutorial:

Ok when I read all three assignments I must wonder, why?  Why do I care?  My husband points out in passing that it is all about set theory.  I stare back at him and blink……

I love the rules we must recite in our sleep:

1.    No repeating elements or groups of elements

2.    No partial dependencies on a concatenated key

3.    No dependencies on non-key attributes

Elements means attributes means in fields

A concatenated key is more commonly called a composite key, but a key is better understood to be something about it that makes it identifiable. 

So in the library world this can relate to library title researches.   The idea that if I look for a work of fiction of a specific genre, the assumption is that there is a collection of titles of in different genre categories.  With categories of authors, publishers, years, holdings….all making up keys, attributes and elements happening at the same time in a simple search for Tales of Two Cities by Charles Dickins.