You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.
You should upgrade or use an alternative browser.
1st normal form
The 1st level of normalization or the 1st normal form deals with data redundancy within each table record. In order to determine if a database table is in the 1st normal form, traverse the table design from column to column within the same row and check if the row is free from redundant data.
Consider the following database table design for bank customers:
customers table
Let's assume that a bank is using such a table to store information about a customer and the type of financial products that the customer has 'purchased' - e.g. credit card, checking account, savings account, etc.
It is quite obvious that there is redundant data in each row - i.e. the product information. Another deficiency is that the design assumes that each customer will have a maximum of 3 products. These problems can easily be removed by normalizing the table to it's 1st normal form. The resulting design will be as follows:
customers table
products table
The normalization results in 2 tables. The product table is tied back to the customer table through the use of a foreign key - in this case, the cust_id field.
See also: 2nd normal form and 3rd normal form
Consider the following database table design for bank customers:
customers table
| column | |
|---|---|
| cust_id | primary key | lastname |
| firstname | |
| ssn | |
| product_1 | |
| product_2 | |
| product_3 |
Let's assume that a bank is using such a table to store information about a customer and the type of financial products that the customer has 'purchased' - e.g. credit card, checking account, savings account, etc.
It is quite obvious that there is redundant data in each row - i.e. the product information. Another deficiency is that the design assumes that each customer will have a maximum of 3 products. These problems can easily be removed by normalizing the table to it's 1st normal form. The resulting design will be as follows:
customers table
| column | |
|---|---|
| cust_id | primary key | lastname |
| firstname | |
| ssn |
products table
| column | |
|---|---|
| product_id | primary key | cust_id | foreign key |
The normalization results in 2 tables. The product table is tied back to the customer table through the use of a foreign key - in this case, the cust_id field.
See also: 2nd normal form and 3rd normal form
Advertising
Advertising: