What is the Difference Between BCNF and 4NF (4th Normalization)?
🆚 Go to Comparative Table 🆚The difference between Boyce-Codd Normal Form (BCNF) and 4th Normal Form (4NF) lies in their criteria for data normalization and the degree of redundancy they allow in a database.
BCNF is an extension of the Third Normal Form (3NF) and has more strict rules than 3NF. For a relation to be in BCNF, it must be in 3NF and satisfy the following condition: For every functional dependency (FD) X -> Y, X must be a superkey in the given relation. BCNF is comparatively stronger than 3NF and allows for more dependency preservation.
4NF, on the other hand, is a further advancement of data normalization. A relation is said to be in 4NF when it satisfies the following conditions:
- It must be in BCNF.
- All multi-valued dependencies in the relation must be resolved.
In simple terms, a relation in 4NF has less redundancy compared to a relation in BCNF, as all multi-valued dependencies are removed in 4NF. In real-world database design, 3NF or BCNF is generally preferred over 4NF due to its practicality and ease of implementation.
Comparative Table: BCNF vs 4NF (4th Normalization)
Here is a table comparing the differences between Boyce-Codd Normal Form (BCNF) and 4th Normal Form (4NF):
| Property | BCNF | 4NF |
|---|---|---|
| Definition | A relation is in BCNF if and only if it satisfies the following condition: For every functional dependency X->Y, X is a superkey in the given relation. A relation is in 4NF if it satisfies the following conditions: It must be in Boyce-Codd Normal Form (BCNF). The table should not have any multi-valued dependency. | |
| Dependency Preserving | Dependency preserving is hard to achieve in BCNF. Dependency preserving is more challenging to achieve in 4NF compared to BCNF. | |
| Number of Tables | The number of tables in BCNF is less than or equal to the number of tables in 4NF. | |
| Real-World Database Design | In real-world database designing, 3NF or BCNF is generally preferred. 4NF is not generally preferred by database designers. | |
| Multi-valued Dependency | A relation in BCNF may contain multi-valued as well as join dependency. A relation in 4NF may only contain join dependency and should have no multi-valued dependency. |
In summary, BCNF is a strict form of 3NF, and 4NF is a further extension of BCNF that restricts multi-valued dependencies. While BCNF is sometimes used in database design, 4NF is less common in real-world applications.
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