Hey all,

Well this is the situation, I am currently studying Computer Science at University and have only studied a little bit of Databases in the past, enough to keep me going when I was doing it, but now I have taken database modules and everyone seems to know what they are doing.

I am really struggling in terms of trying to understand how to normalize a database!?!? I have looked online at so many different examples, but they all seem to say the same thing, but I do not understand...I think this is right:

-To get a database into 2nd Normal Form you need to remove all functional dependencies.

-To get a database into 3rd Normal Form you need to remove all transitive dependencies.

Hopefully I have understood this correct!?!? But the thing is, I understand the concept of this, but I do not understand how to actually apply this...and I have searched and searched on the Internet for just a simple beginners guide to this...and it is driving me mad on how complex some 'simple' guides are??

There was an example given today, which was this...

If we know this:

Relation Name: Contacts
Attributes: Name, Room, Telephone, email
Dependencies: Name -> Telephone
Room -> Telephone
Name -> email

Turn this into 3rd Normal Form. I cannot do this to save my life for some reason...I cannot understand how to know what the functional dependencies are??

I mean, from this i can gather that Name -> Telephone, Email, and that Room -> Telephone, but which ones are partially dependent and how do you tell?

If anyone can please PLEASE explain and talk me through this and give a simple guideline on how to turn a table into a 2NF, given a set of dependencies I will be forever grateful!

Thanks you in advance guys, most appreciated!

Ben

try http://r937.com/relational.html

note that room does not necessarily determine telephone

it might've, back in the day, when all there was was land lines

but i would venture that a person's contact information might include a cell phone today

as for your question about 2NF, if you don't have a composite primary key, then as long as you don't have any column containing multiple values (like a comma-delimited list), then you're automatically in 2NF

Thank you for the reply, I shall read through that website now for some advice and help on the subject!

I think this was a bad example, there are a couple more that were given today....

Could you please help me identify the "Partial Dependencies"...this is what I cant really seem to do, I now kind of understand what to do, it's just identifying the partial dependencies that i cant do...can someone please talk me through identifying them in this example:

R1
a, b, c, d, e, f, g, h
a -> b
a -> c
d -> e
a -> f
d -> f
f -> g
e -> h

Which ones are partially dependent and why??
How would you organize this into 2nd Normal Form??

Thank you once again

sorry, i don't do partial functional dependencies, or academic exercises, either

i just build tables

lol...if anyone out there can help me PLEASEEE help lol

That website link you gave me is awesome and explains it in simple terms, thank you very much!

I think, thinkkk that this is the solution to the above problem...

table 1:
(PK) A
B
C

table 2:
(PK) D
E

table 3:
(PK) A
(PK) D
F
G

If anyone out there can tell me this is correct or where i've gone wrong, much appreciated!

Cheers

Wow in all seriousness I have spent quite a while tryin to get in terms with all of this, and after reading that simple website, I think I am starting to understand it....well when someone replies to my thread if i am right or not it would be a great help to see if i have understood it....

The only thing for me now is....

What on earth do you do for an example like this!?!?

R1
a, b, c
a -> c
b -> c
c -> a
c -> b


Do you simply do:

Table 1:
(PK) A
C

Table 2:
(FK) A
(PK) B
C

This is a confusing one, if I have got the first one right, then I think this is the last obstacle to understand! Im looking forward to a reply to help to give myself peace of mind

Cheers