dajjal619
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A car hire firm wants to store data about its cars and the customers that hire them. When a
customer hires a car, the hire is given a Hire_ID. A customer can hire more than one car under the
same Hire_ID. Each car can only be hired to one customer at a time. Each hire is made by a salesman.


The car hire database is currently in 1NF. Convert it to 3NF:

HIRE_CARS(Hire_ID, Hire_Date, Hire_Cost, Salesman_ID, Salesman_FirstName, Customer_ID,
Customer_FirstName, Customer_LastName, Customer_Email, Car_Reg, Car_Make, Car_Model)
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Know Your Enemy
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What exam board is this?
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dajjal619
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(Original post by Know Your Enemy)
What exam board is this?
AS LEVEL AICT . 9713. Cambridge International. could you help me?
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Know Your Enemy
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(Original post by dajjal619)
AS LEVEL AICT . 9713. Cambridge International. could you help me?
I wish I could but I'm doing WJEC and what you've described isn't in our spec. Sorry.
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Cyberspace
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The following resource might help you:

https://beginnersbook.com/2015/05/no...ation-in-dbms/
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winterscoming
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(Original post by dajjal619)
A car hire firm wants to store data about its cars and the customers that hire them. When a
customer hires a car, the hire is given a Hire_ID. A customer can hire more than one car under the
same Hire_ID. Each car can only be hired to one customer at a time. Each hire is made by a salesman.


The car hire database is currently in 1NF. Convert it to 3NF:

HIRE_CARS(Hire_ID, Hire_Date, Hire_Cost, Salesman_ID, Salesman_FirstName, Customer_ID,
Customer_FirstName, Customer_LastName, Customer_Email, Car_Reg, Car_Make, Car_Model)
Database normalisation is about the logical grouping of Attributes into Entities in order to reduce redundant data. (i.e. unnecessary repetition of the same data - remember that each row in any table exists on its own, so for 3NF you want to avoid having items of data which are repeated across multiple rows).

An Attribute is a single item of data which can be stored in a database. E.g. an ID number, a name, a postcode, a house number, a ticket cost, etc. Your problem statement already lists all of the attributes that you need to model, so this part is done for you.

An Entity is a logical grouping of Attributes, which means an entity is a 'thing' about which data can be stored in your database.

Read your problem statement carefully and look at any Entities which it might suggest (i.e something which might be represented by one or more of those attributes when grouped together). Consider that Entities are often represented by Nouns in the English language - so have a look at those words in your problem statement which are considered to be Nouns in the English dictionary - that makes them possible candidates to represent entities in a database.

Once you have a list of entities, the next step is to consider which of your attributes, if any, might belong to those entities. Note - in the process of writing down those entities, you may find that some of the entities you'd previously written down might not be needed. Similarly, you might look at your list of attributes and decide that they do not "belong to" any of your entities - in which case, that means there's the need for a new entity which you haven't considered yet,

(Note - sometimes entities are not just plain/simple nouns, sometimes you need to create an entity for the purpose of modelling a relationship, whose name might be more complex, but you can start with simple nouns to begin with)

Lastly, remember the golden rule of 3rd Normal Form: "Every attribute depends upon the Key, the whole Key, and nothing but the Key".
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dajjal619
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(Original post by Cyberspace)
The following resource might help you:

https://beginnersbook.com/2015/05/no...ation-in-dbms/
Thank you big boss!!
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dajjal619
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(Original post by winterscoming)
Database normalisation is about the logical grouping of Attributes into Entities in order to reduce redundant data. (i.e. unnecessary repetition of the same data - remember that each row in any table exists on its own, so for 3NF you want to avoid having items of data which are repeated across multiple rows).

An Attribute is a single item of data which can be stored in a database. E.g. an ID number, a name, a postcode, a house number, a ticket cost, etc. Your problem statement already lists all of the attributes that you need to model, so this part is done for you.

An Entity is a logical grouping of Attributes, which means an entity is a 'thing' about which data can be stored in your database. For example, a database about a Theme Park might include the following entities

Read your problem statement carefully and look at any Entities which it might suggest. Consider that Entities are often represented by Nouns in the English language - so have a look at those words in your problem statement which are considered to be Nouns in the English dictionary - that makes them possible candidates to represent entities in a database.

Once you have a list of entities, the next step is to consider which of your attributes, if any, might belong to those entities. Note - in the process of writing down those entities, you may find that some of the entities you'd previously written down might not be needed. Similarly, you might look at your list of attributes and decide that they do not "belong to" any of your entities - in which case, that means there's the need for a new entity which you haven't considered yet,

(Note - sometimes entities are not just plain/simple nouns, sometimes you need to create an entity for the purpose of modelling a relationship, whose name might be more complex, but you can start with simple nouns to begin with)

Lastly, remember the golden rule of 3rd Normal Form: "Every attribute depends upon the Key, the whole Key, and nothing but the Key".


Thanks for taking the time out to write this beautiful piece of info.
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