Database Design and Administration
Today we covered Milestone 3 some more, before class I was playing around with Microsoft SQL Server, creating tables and what not, getting to grips with the program.
During class we watched a video on indexing – and where given some Lynda videos to to look at some small activities.
Todd also briefly covered the classes he teaches next semester with us after class right now I will work on some more Milestone 3 in the library before the library closes at 5pm.
Over the study break we had Milestone one to work on – out first proper assessment for the DAT 601 class.
Being There drones – for milestone one we where to draw a conceptual model – fill in data dictionary – and also write down the business rules.
So In the first week of the holidays – I came down with a really bad cold which put me out of action for a few a whole week – so during that week over work was done, as I got better in the second week I was coming down to the NMIT Library and working on milestone one.
Then hand in date for Milestone one was the first week back from out study break – it was a very long assessment and I can see why Todd, gave use 3 weeks to work on it. It was a lot more work then I Thought – but I did manage to get it all handed in by Friday Midnight without any stress.
Now we will start with getting into milestone two and learning how to make physical databases.
Today we are starting to use Microsoft SQL and creating a physical database – we first covered what we can do with it how SQL came about, we are gonna start by making some tables .
We first talked about creating tables from the notes in week 8 – we where also given some exercises to do in our own time.
we also covered relation databases and did a small class discussion with it.
We where given some homework and exercises to do over the next week.
The Transformation Game
Conceptual to logical.
The rules:
Today we covered the problems that you can run into when you are designing ERD’s, these are called connection traps here I will cover two types.
Fan Trap:
Where two entities have a one to many relationship that fan out from a third entity. I have researched online and found this example.
“Fan trap occur in a situation when a model represents relationship between entity types however a path between certain entity occurrences is ambiguous
Example: (Staff)-1:N-has-1:1-(Division)-1:1-operates-1:N-(Branch) in this model it may be impossible to determine the branch a staff belongs to, in the situation when staff belong to division having more than 1 branches.
Restructuring the model resolves trap (Division)-1:1-operates-1:N-(Branch)-1:1-has-1:N-(Staff).”
Chasm Trap:
“This type of trap is a relationship between entities, but these pathways don’t exist
Chasm trap occur when a model suggests relationship between entity types however a path between certain occurrences does not exist.
Example: (Branch)-1:1-has-1:N-(Staff)-0:1-oversees-0:N-(PropertyForRent)
Because Staff relationship to PropertyForRent is with optional participation (0:1) for staff the path for Branch to PropertyForRent may not exist. Solution to this would be direct relationship between Branch and PropertyForRent with mandatory participation”.
We covered a few topics today – was very informative we covered reports, cardinality, participation, and weak and strong entities.
Report Template:
We where given a template for our milestone one – this was nice, since it outlined everything we needed for the report I found it extremely helpful after out summer break..
Cardinality Constraints:
Cardinality – this is the number of instances that an entity can have with one another, for instance, One baby can have one child, there are four possible cardinality constraints.
Participation Constraint:
This specifies a minimum amount of relationships a entity can have – so every connection of a relationship must have a participation constraint, but participation constraints don’t apply to relationships.
Weak entity and Strong entities:
The second week in DAT601 and I must admit I am learning a lot and really enjoying it! at the moment I am reading through this really good power point presentation and entity relationship diagram we have been supplied with in class.
Entity! – what are they?
Entity Type?
Entity Set?
So what does this all mean? well to me I think it means that is an object that we want to store information about and that they are usually recognizable and they are either, persons, places and even events that relevance to the database!
Attributes describe the properties and are represented by ovals and are then connected to the entity by a single line, for instance, a student would have the following attributes.
I will go into more detail in my next blog once I have gone over the different types of attributes ( Composite, Single-Valued, Multi-Valued, Derived and Stored) and I’ll also talk more about Keys! just have a bit more reading to do!
This week in DAT601 – we covered more of the power point went over some more about relationships – Binary, Ternary and even the Quaternary relationships.
We also went into Unary relationships, or known as recusive relationships this is a relationship will particapte more then once in the same role, so for instance an employee is supervised by an employee who in turn is the supervisor.
within relationships there are four possiable categories or Cardinality Constraints:
This was a good lecture and it gave me more understading and built apon my understadning of relationships within database’s alot more!
Our group also got a lot more done with the practice project, which was fun getting together and learning from one another. a few more diagrams where completed Ill hopefully have a blog post about that once I get some pictures of them.
Today we covered more about the conceptual design, we went into more detail about entitiy’s and ERD’s
We got put into our groups ( The groups we made for our practice report) – and then sent down to the Queen’s Gardens to look for nouns, we where given 15 minutes to hunt these out, from there we went back to class and filled them out all together on a google doc.
This was a really cool way of doing things and a nice interactive way of learning, plus who could of known there was that much stuff in the little queens gardens!
After we had made the list, Todd drew on the whiteboard as put the entities into categories, I learn’t a lot from Friday’s lesson and I look forward to learning more!
Introduction day into DAT601:
Today’s lecture was our first for DAT601, we started off by going over the course outline, what each week will be and what we will cover, we talked about passing the course with attendance, participation and actually doing the work.
We talked about Peter Chen, Edgar F. Codd and Christopher J. Date and how they shaped databases.
We are have been put into small groups of four or five, within these groups we are doing a practice project, which I think is a great idea! since we can also use that material for out proper projects later on in the semester! – we have some work that is due this Friday, storyboards for our game, and it will also be good to use this time, to get used to working in teams again!
There was a pretty informative presentation today, which also covered the course outline and also some information we covered last year in DAT501 – it was a good refresher, it was also filled with heaps of other information, it was a nice smooth introduction into this semester and the work load we can expect.
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