Second Normal Form (2NF)
Second Normal Form (2NF)
The concept of remove the delicacy of data comes in the Second Normal Form (2NF).
A. It should meet all the requirements of the first normal form.
B. It should remove subsets of data that apply to multiple rows of a table and place them in separate tables.
C. It create relationships between these new tables and their predecessors through the use of foreign keys.
The First Normal form deals with the atomicity whereas the Second Normal Form deals with the relationship between the composite key columns and non-key columns. To achieve the next progressive level your table should satisfy the requirement of First Normal Form then move towards the Second Normal Form.
Let's introduce a Review table as an example :
| Item | Colors | Price | Tax |
| Pen | red | 2.0 | 0.20 |
| Pen | blue | 2.0 | 0.20 |
| Scale | red | 2.0 | 0.20 |
| Scale | yellow | 2.0 | 0.20 |
| Bag | blue | 150.00 | 7.80 |
| Bag | black | 150.00 | 7.80 |
Table is not in Second Normal Form because the price and tax depends on the item, but not color.
| Item | Colors |
| Pen | red |
| Pen | blue |
| Scale | red |
| Scale | yellow |
| Bag | blue |
| Bag | black |
| Item | Price | Tax |
| Pen | 2.0 | 0.20 |
| Scale | 2.0 | 0.20 |
| Bag | 150.00 | 7.80 |
Tables are now in Second Normal Form.
In the next section, we will take a look on the Third form of Normalization.