4. 1NF Example
Reminder: Rules for first normal form
- There are no columns with repeated or similar data
- Each data item cannot be broken down any further.
- Each row is unique i.e. it has a primary key
- Each field has a unique name
Which of these tables are NOT in first normal form?
|Mr||Tom||Smith||Tom Smith||42 Mill Street||London||WE13GW|
|ID||IP Address||username||last accessed||Activity||Result||active|
Table 1. This is not in 1NF. There is no primary key defined and so this record cannot be guaranteed to be unique. Also Full name is redundant - data is not atomic - as it is simply a combination of Firstname and Surname.
Table 2. This is in at least 1NF. It has a primary key identified by the underline. The data is atomic. Each field has a unique name. There are no repeat data.
Table 3. This is not in 1NF. It has a primary key, so it passes that test, data is atomic - tick in the box, but the colour the shoe can come in is being repeated - and furthermore the fields have the same name - so not in 1NF
Table 4. This is in 1NF as it meets all the rules for the first normal form.
Question to ask yourself to spot 1NF
- Does it have a primary key
- Are each field name unique
- Is the data atomic
- Are there repeating / redundant fields.
Challenge see if you can find out one extra fact on this topic that we haven't already told you
Click on this link: First Normal Form
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