BIT320 Remix — Normalization

November 17, 2005

Looking at who’s looking at you

Topics:

Yes, I know you all want to know. You want to know who’s looking at you so that they can look at them looking at you, you looking at them looking at you. Confused yet? Yeah I am too ;)

Matt happened to be trying to get a tracker to work on his blog. I commend his efforts because, yes wanting to look at who’s looking at you when you are looking at…yes that again. HAHA. Anyways, on my own blogger, I happened to use, Webstats4u.com. I found it from a friend’s xanga or blog.

The nice thing is it tracks all sorts of things. If you look at my blogger tracker stats, It keeps things like, how many, the countries, what time during the day, how they connect, through what websites they come from, and what kind of browzer they use. So cool eh.

But the one problem with our blogs is that it doesn’t let us edit the http and layout of the blog. So what you have to do, is they will send you the links in an email that you need to have on your blog. The only way the tracker will work is if you link back to the main page of webstats4u.com, not just your own tracking site. You know, you link me while I link you linking me linking you and I coun’t your stats. Got it? get it? good ;)

In Shady Waters, 11/17/2005 | Original | Archive | Post to del.icio.us | Technorati

October 31, 2005

Normalization Question: Problem 8 from Ch.1

Topics:

I have a question from Ch.1 (normalization-pg.7). Why isn’t the primary key a combo of inv.# + Cust ID + Part #? It shows only inv# + part # as the primary key. Like I understand that the inventory will have the cust ID but then thinking about the example with customer and stock information, we said tht the primary key should include both cust ID and stock ID since we have info on those two. So here we have info on these 3 topics - so why dont we include all in the primary key?

 

Thank you.

 

In supriya, 10/31/2005 | Original | Archive | Post to del.icio.us | Technorati

October 25, 2005

Normalization Problem 8

Topics:

Zeenah asked about Normalization Problem 8, on page 12 of the CP:

After putting the problem into 3rd NF, one of the primary keys is Inv #. I had put Cust # as mine instead of Inv #, but then I started thinking and wouldn’t they be subsitutable?

I think this has a lot to do with assumptions. I personally chose Inv# and not CustID. My logic was this: A customer can purchase stuff on more than one occasion. For each unique date+customer, there is an Inv#. So, let’s say customer 42 bought something in 11/63. This would generate an Inv# different than 14. Therefore, custID could not uniquely identify transactions.

However, like I said, I think this has to do with what you assume to be true. I am assuming that customers can buy on different dates, and that invoice numbers are associated with customers AND dates. You could assume that customers only buy on one occasion, and therefore Zeenah’s logic is correct.

In jb's blog, 10/25/2005 | Original | Archive | Post to del.icio.us | Technorati

Database Normalization

Topics:

Database normalization guide detailing how to optimize tables.

In del.icio.us/kevlers, 10/25/2005 | Original | Archive

October 24, 2005

The Curve — Why Blogstar gets it

Topics:

So, with some amusement, I read the various posts over the weekend about the curve. I say “with amusement” because they popped up in the middle of a presentation I was doing on the class remix. Talk about having to be quick on your feet.

At any rate, SuperMatt started it off with:

Our Bit320 class has less than 15 students in it. This is great for learning, but terrible for grading. Most classes have many more people enough to get a large enough sample to allow for a bell curve.

TigerLilly fired back with:

Also, I think the curve does not encourage group work because basically we have to fight for a spot in the ranking. It is not avoidable with the mandatory group work but besides that, I have no incentive to help someone else out.

and finally, our pal Shady resonated to this last sentiment:

Maybe but then what are they doing trying to get us to compete with each other, if they really want us to work together. It’s like MO said:

Rewarding B when hoping for A.

And lets all be honest here, this isn’t a problem. These are opinions. OPINION SLUG!

Then, perhaps unaware of this fracas, or perhaps just hoping it would go away and purposely moving on to a productive topic, Blogstar chimes in with:

Repeating groups occur when you have mutiple columns of the same attributes.

Responding to Tigerlily’s observation (perhaps written after her “I’m not sure I should share information post”):

As I have been looking over my notes, the repeating groups concept doesn’t make sense to me anymore. Can someone quickly explain it?

My observation is this. We are at a stressful point in the semester. People realize they are going to be evaluated, and they want to make sure they get an evaluation that matches their true capabilities. They are worried that they will somehow give away “the secret” to their success.

Let me attempt to relieve these concerns. The test is only 10% of the grade. Blogging is 36% of the grade. You are making many more points by blogging than by taking the test. The blog posts that I consider the most valuable are posts like Blogstar’s (as I write this, Kevin makes a similar post) where the student makes a contribution to the class’s knowledge about the topic covered.

I will grade the blogging portion based on quantity and quality. Contrary to Tigerlily’s and Shady’s observations, the lion’s share of credit in this course is given based on your contribution to the class knowledge. The person who scored the lowest on the exam last year scored an A for the course because he did incredible projects and really contributed.

Remember this point.

In Blogonautic Solutions, 10/24/2005 | Original | Archive | Post to del.icio.us | Technorati

Normalization Problem Help

Topics:

Page 12 of 17 on Normalization, Problem #8..After putting the problem into 3rd NF, one of the primary keys is Inv #. I had put Cust # as mine instead of Inv #, but then I started thinking and wouldn’t they be subsitutable? I feel like they would both be candidate keys and you can just choose one. A customer will identify the Inv # and the Inv # can identify a customer. I am only thinking this way because for example, Cust ID 42 has two Inv #’s but both are 14. Therefore couldnt we use it interchangably? If the Inv #’s were different I realize that we couldnt. I hope this makes sense and someone can answer my question!

In zee124, 10/24/2005 | Original | Archive | Post to del.icio.us | Technorati

October 23, 2005

Repeating Groups

Topics:

Repeating groups occur when you have mutiple columns of the same attributes. For example if you’re looking at data regarding a parent and his/her children it should be a ROW for each child as opposed to putting the parent in the first column, the 1st child in the second, the    2nd child in the third column etc.  This is a link I found that may help you out as well.

In The Blogstar, 10/23/2005 | Original | Archive | Post to del.icio.us | Technorati

Repeating Groups?

Topics:

As I have been looking over my notes, the repeating groups concept doesn’t make sense to me anymore.  Can someone quickly explain it?

In Tigerlily's Blog, 10/23/2005 | Original | Archive | Post to del.icio.us | Technorati

September 19, 2005

Normalization 10

Topics:

Pink Footsie makes the following observation regarding normalization problem 10:

I kept the due date instead of the days and wrote up the second to last 3NF relation as [Date, Type] -> [Date Due, Cost] since date due is a function of the date rented out and the type of the movie as my assumptions.

I think this solution resolves from not considering the pragmatics of the scenario. Under Pink Footsie’s interpretation, you have to ask yourself how the store would come up with the due date. Basically, people would be oblighed to somehow generate a due date each time they input a new video rental based on the date. How?

Under the proposed solution for Normalization 10, the number of days you can keep the video based on type is the key piece of data the store retains in the database. That way, given date and type, it’s easy to calculate the due date.

In Blogonautic Solutions, 09/19/2005 | Original | Archive | Post to del.icio.us | Technorati

Problem 10 Normalization exercises

Topics:

As I was doing Problem 10 in the cspk I realized that with the more complicated problems your answer is very dependent on the assumptions that you make. For example to get 3NF in that example I kept the due date instead of the days and wrote up the second to last 3NF relation as [Date, Type] -> [Date Due, Cost] since date due is a function of the date rented out and the type of the movie as my assumptions. Is this okay as well? The cspk examples are also online.

In Pink Footsie, 09/19/2005 | Original | Archive | Post to del.icio.us | Technorati

September 18, 2005

Rules of Data Normalization

Topics:

Includes some great examples if you still can't grasp some of the NF terms

In del.icio.us/jbartko, 09/18/2005 | Original | Archive

Non-Normalized Databases 2

Topics:

In response to Matt’s question on non-normalized databases,”wouldn’t it be better to just create a report/query that pulled the data from a normalized database and arranged the data however it would be most useful to you? Or would this just be creating more work for yourself?” I think you’re making one big assumption; that the database already exist.  It does sound feasible to create a report/query if you already have the information in a database. However, if you’re in the process of creating a new database that doesn’t call for normalization then yes you would be creating more work for yourself. So really it depends on the particular situation.

In The Blogstar, 09/18/2005 | Original | Archive | Post to del.icio.us | Technorati

Non-Normalized Databases

Topics:

So I was thinking about the conversation we had in class about where a non-normalized database would be useful. And I agree that in a historic context, having the data arranged in this way would be useful. However, wouldn’t it be better to just create a report/query that pulled the data from a normalized database and arranged the data however it would be most useful to you? Or would this just be creating more work for yourself?

In Matt's Musings, 09/18/2005 | Original | Archive | Post to del.icio.us | Technorati

Avoid Uncategorized like the plague

Topics:

Zee124 is but the latest to fall into the trap of the Uncategorized post. Avoid that non-category like the plague. If you must have a default category, use classquestions.

On the substantive topic of Z’s post:

It’s right in suggesting that we do the problems on our own first without looking at the answer, but sometimes I feel like I interpret things differently. For example the problem involving the movie receipt, I figured that the Cost of a movie could be derived from the type of movie it was. Then I remembered the difference between deriving and transitive and realized I was wrong. It’s going to take a lot of practice before normalization comes naturally.

The simple answer is yes. Also, recall that some of this is interpretation. If you feel that you are just interpreting differently but correctly, raise that issue as a classquestions with, perhaps in this case, normalization, thrown in.

In Blogonautic Solutions, 09/18/2005 | Original | Archive | Post to del.icio.us | Technorati

September 16, 2005

Normalizing my life

Topics:

I like this website for Normalization. It seems like an idiot’s guide but those are my favorite books, of which there are many on all kinds of subjects, btw. I think the exercise we did in class was very helpful. I’m not much for definitions so when I actually get to see what it means I’m a very happy camper. I love puzzles. I’m weird like that.

In Pink Footsie, 09/16/2005 | Original | Archive | Post to del.icio.us | Technorati

Databases and Normalization

Topics:

Here is another resource to learn more about Normalization and Databases

In del.icio.us/supriya, 09/16/2005 | Original | Archive

Problems with posting blogs

Topics:

I am having a problem posting my blog. It gives me the following error message:

Warning: Cannot modify header information - headers already sent by (output started at /home/highoct/public_html/wp-inst/wp-includes/comment-functions.php:516) in /home/highoct/public_html/wp-inst/wp-admin/post.php on line 110

Has anyone else had the same problem? Or can someone explain to me whats going on?

Thank you.

In supriya, 09/16/2005 | Original | Archive | Post to del.icio.us | Technorati

Response to Transitive Dependency

Topics:

Response to the question on Transitive dependency:

I was looking over some notes and I am still unclear of what transitive dependency means. Can anyone help me out on this?

A transitive dependency occurs in a database when the value of a non-key attribute is dependent on the value of another non-key attribute in that table.

While looking for articles to explain transitive dependencies better, I came across a rather good article that explains with an example. To view the article, click here and then scroll down to Third Normal Form.

 Hope this helps!

 

In supriya, 09/16/2005 | Original | Archive | Post to del.icio.us | Technorati

September 15, 2005

what is transitive dependency?

Topics:

I was looking over some notes and I am still unclear of what transitive dependency means. Can anyone help me out on this?

In Tigerlily's Blog, 09/15/2005 | Original | Archive | Post to del.icio.us | Technorati

September 14, 2005

What exactly is the superkey, and candidate key?

Topics:

Ok, now I know the article said to read the following definitions a couple times in order to get the idea but I still don’t.  I understand the idea behind the primary key but can someone please elaborate more on the definitions of the superkey, and candidate key.  Thanks

In The Blogstar, 09/14/2005 | Original | Archive | Post to del.icio.us | Technorati