What is BCNF in DBMS
As Key candidate becomes an attribute or a Attribute combination denotes the one Identify the data record clearly (i.e. form a primary key).
The BCNF only needs to be used if several key candidates are present and look at this partially overlap. If there is only one candidate key in the relation or if there is no overlap in the case of several candidate keys, the relation is automatically in the BCNF.
Boyce Codd normal form definition
A relation type is then in Boyce-Codd normal form (BCNF)if each relational-type determinant is a candidate key. The Boyce-Codd normal form is the highest normal form based on functional dependencies. A relation (table) that is in Boyce-Codd normal form (BCNF) is also at the same time in the third normal form (3NF).
Boyce-Codd Normal Form (BCNF) example
The starting point for the following consideration is the table, which picks up on the invoice example and has been expanded to include the warehouse location column. The warehouse location indicates where the item was stored in the warehouse.
|ReNo||Item No||Storage location||number|
The composite key candidates are ReNo–Item No and ReNo–Storage location.
Between Item No and Storage location there is a functional dependency that has nothing to do with the invoice number, so the relation is in 3rd NF, but not in Boyce-Codd normal form.
The attribute Item No here is the determinant for the storage location, but the attribute Storage location is only part of a key candidate and is therefore functionally dependent on the attribute Item No. The same applies to the opposite direction, as the item number can also be determined via the storage location.
The dependency is made possible by a Distribution of the data solved in two tables. This creates two new tables from the original table, which are linked by a primary key.
New table: "Invoice Article"
New table: "Article storage location"
|Item No||Storage location|
- Why do people use sunscreen when tanning
- Why does inorganic chemistry feel so difficult?
- How competitive is industrial design
- What is a white liberal
- How good is it to work in a startup
- How many Singaporeans visit UC Berkeley
- How can public transport integrate urban cycling?
- Most Americans are intellectual
- What are some examples of a database
- How do places get their names
- Is there a legitimate freelance job online
- What goes well with chia seeds
- Why is Bob Ross famous
- What caste is Ramgharia Sikh
- Where can I buy powerful spiritual oils
- Who sponsors Manchester United
- Who are SAP ERP customers
- When did people start using general courtesy?
- Is an arranged marriage really a marriage?
- What are acts of self-sacrifice
- Why are modern Greeks viewed this way
- How does technology help students learn
- What fuel is called black gold
- What is a factory warranty
- Michael Jackson was above the law
- Do clothes affect who you are
- How do I make vegan burgers
- What do you think about suicide 2
- How can a teenager publish research
- How does emerald melt
- What is absolute advantage and comparative advantage
- Are women with Borderline Personality Disorder overweight?
- What is the other animal of the horse
- What is paradise for you