How does 2NF decompose?
How does 2NF decompose?
- Consider the following relation:
- First:
- Now we can test for 2NF violation :
- Decomposition: remove the a → b violation:
- Test R1 and R2 for 2NF violation : ( R1 will be in 2NF by the way we constructed it)
- Decomposition: remove the d → e violation:
What is 2nd normal form in database?
A relation is said to be in the 2nd Normal Form in DBMS (or 2NF) when it is in the First Normal Form but has no non-prime attribute functionally dependent on any candidate key’s proper subset in a relation. A relation’s non-prime attribute refers to that attribute that isn’t a part of a relation’s candidate key.
How do you know if a relationship is 2NF?
A relation is in 2NF if:
- Relation is in 1NF (i.e., every attribute is atomic), and.
- every non-key attribute is fully functionally determined by every key of the relation. In other words: You cannot find a non-key attribute that is functionally determined by only a (proper) subset of a key.
How do you find 2NF and 3NF?
If the candidate key comprises of only single attribute and relation is in 1NF then it is already in 2NF….Difference between 2NF and 3NF :
| S.NO. | 2NF(Second Normal Form) | 3NF(Third Normal Form) |
|---|---|---|
| 6. | The goal of the second normal form is to eliminate redundant data. | The goal of the third normal form is to ensure referential integrity. |
How check 2NF in DBMS?
2NF: In 2NF, we need to check for partial dependency. CD is a proper subset of a candidate key and it determines E, which is non-prime attribute. So, given relation is also not in 2 NF. So, the highest normal form is 1 NF.
What is difference between 2NF and 3NF example?
For instance, in 2NF, non-prime attributes are not dependent on prime (or key) attributes, but a non-prime attribute can depend on another non-prime attribute. 3NF eliminates this possibility as non-prime attributes are only dependent on the super key of the relation.
