11 replies to this topic

[Coolman]

Well I have been doing my revision and the only thing I'm slightly bamboozled at is the process of getting from UNF to 3NF. Could anybody tell me any tips or anything that is handy on working it out before the exam tomorrow ?

[kingding]

what exactly do you need help with ?

[Coolman]

well after you get to 2nf how exactly do you know how to get to 3nf and how do you know when to carry over the foreign key's to the new table.

[Tiger]

well after you get to 2nf how exactly do you know how to get to 3nf and how do you know when to carry over the foreign key's to the new table.

I dont i used to be really good at normalisation but did one write now n i dont know what's wrong with it.
I chose a different primary key az shown in the answers. Its the 2006 specimen paper. I chose leader to be the primary key rather than activites. Could anyone tell me what to do?

[kingding]

Rite:
to get to 1NF, identify repeating groups and put these in a seperate entity, with the primary key of the intitial entity, therebye creating a link.

to get to 2NF, identify any partial dependencies. Look at the attribute/field that the other fields are dependent on, and take these fields AND the attribute (that is part of the key) to another entity. The key will be the attribute that the other attributes are dependent on. This will be related to the previous entity. The occurence of the (key) attribute in the previous entity will be a foreign key(*).

to get to 3NF, do the same as this but with the attribute that others are dependent on, not part of the primary key.

basically, when in 2NF and 3NF, and when splitting attributes into other entities, the initial entity is where the foriegn key will be, and is the "many" side of the relationship.
dunno if that helps

tiger, what was the question that you were talking about in the specimen paper??

[Tiger]

tiger, what was the question that you were talking about in the specimen paper??

Question 16

[kingding]

can you send me the link to the answers
cheers

[Tiger]

can you send me the link to the answers
cheers

http://www.sqa.org.uk/files_ccc/InfoSys_H_SQP.pdf

[Coolman]

thnx kingding

[kingding]

rite so;
to get into 1st normal form, you have to take out the attributes from activity downwards, with member no. as a foreign key. The primary key in the other entity is a compound/concatenated key with activity and member no. (which is also a foreign key). Activity is there because each activity is specific and the evening, venue, and leader are dependent on it.
to get into second normal form, you need to locate partial dependencies, by looking for attributes that are only dependent on part of a compound/concatenated key. Since there is a compound key in the new entity, there will only be a dependency in that one. It can be seen that leader, leader number, cost, and venue are dependent on activity. Take this out, form a new entity, and leave a foreign key in the second entity.
to get into third normal form, locate transitive, non key dependencies, and take them out and put them into another entity. Leader telephone is dependent on leader, and so create a new entity with these in it. In the entity with activity, put the foreign key for leader name.

[shaunaaa]

UNF

1) Write down all the attributes in a vertical list
2) Select primary key
3) Indent repeating group


1NF

1) Put repeating group into new relation/entity/table
2) Select a primary key for your new table
3) Identify any foreign keys_{foreign key: a key that is a primary key in another table}


2NF
_{Hint: Check each part of this seperately for the different tables}

1) If there is a compound primary key, then seperate the attributes of the table that are only dependant on PART of the primary key.
2) There attributes should be put into a new table.
3) Select a primary key for your new table.
4) Identify any foreign keys.


3NF
_{Hint: Check each part of this seperately for the different tables}

1) If there are any attributes that are dependant of other attributes that are NOT primary keys, then remove these to a new table.
2) Select a primary key for your new table. You may have to create a surrogate key. _{surrogate key:a key that is specifically made up to be uniquely identify a record, aka be a primary key.}
3) Identify any foreign keys.

[megan deenna]

Well I have been doing my revision and the only thing I'm slightly bamboozled at is the process of getting from UNF to 3NF. Could anybody tell me any tips or anything that is handy on working it out before the exam tomorrow ?

yeah same!!