Hi guys, first post here, found it from a Google search. I'm working on a University assignment and have come across a problem quite early on which stops me from making my ERD's and of course the SQL. Unfortunately, none of my peers have attempted this so I have no feedback and am thus posting here.
The spreadsheet of data we have been given is for books, journals & conferences where each may have one to many authors, and each author is from a different country. I cannot figure out what dependency the country has other then each individual author which makes it quite messy. Below is my attempt, if anyone can offer any hints or even point me in the direction of some reading material it'd be greatly appreciated. (PS. PubNo is the Publication Number from 1 onwards)
PubNo -> Author1, Author2, Author3, Year, Title, Conference, Journal, ISBN
Author1 -> Country
Author2 -> Country
Author3 -> Country
A lot depends on what you are trying to do, and which method(s) you are planning to use. There are many ways (methodologies) to create ERDS, and all of the ones I can think of will work for a simple example like this.
What are you hoping to get from us? What methods have you been taught so far (specifically, which ERD modeling methodology or methodologies are you using)? I suspect that the reason no one has responded is that we don't have enough information yet to give you any kind of useful response.
Now, ERD's, Im really not familiar with alternate methods, but the one we use can be loosely described as having entities, withitn which are all the attributes, with primary/foreign keys marked, and are linked to other entities by a one to one, one to many, many to one, etc relationships.
Thats all I can describe really?
What I was hoping for from you guys is just a yes or no with regards to the functional dependencies I have posted up, as form there on, Im sure I can give the ERD's a crack. Im just very confused about the correct-ness of the dependency of a country to each individual author (Looks v.messy)
If anyone requires more information regarding this Id be glad to post it up.
First step would be to identify all of the "things" you need to track. Authors, countries, the relationship between an author and a country (those are three different things in my mind). This is your set of entites.
Next step is to identify which of those entities refer to other entities. For example the author-country relationship needs to refer to both the author and the country entities. These references will require foreign key constraints later in the process.
Once you've got a working set of attributes, you need to decide which attributes within an entity will uniquely identify just one member of the entity set. This attribute or combination of attributes becomes the entities primary key.
At this point, you can construct the foreign key constraints, and you've got enough to start an ERD.
This is a vastly simplified process. I've skipped a lot of steps that aren't germane to your example in the interest of keeping things simple, but I think that is enough to get you started using any of the methodologies that I use.