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Understanding Multi-valued Dependencies and Fourth Normal Form, Slides of Database Management Systems (DBMS)
The concept of multi-valued dependencies (mvd) and the fourth normal form (4nf) in database normalization. It covers the definition of mvd, its differences with functional dependency (fd), testing for mvd, armstrong's axioms for mvd, a quick review of normal forms, and an example of 4nf. Mvd allows for multiple values of an attribute to depend on a set of attributes, while 4nf ensures that there are no nontrivial multi-valued dependencies in a relation schema.
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2012/2013
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Higher Normal
Forms
What I Will Talk About
- Define Multi-valued Dependency (MVD)
- MVD v. FD
- Armstrong's Axioms for MVD
- Quick Review of 1NF, 2NF, 3NF, BCNF
- Fourth Normal Form (4NF)
MVD v. FD
MVD v. FD (cont)
Functional Dependency:
**_1. Every FD is a MVD.
- FDs rule out certain tuples_** _ If X --> Y then we can't have two tuples_* with the same X values but different Y values.
How To Test for MVD
How To Test for MVD (cont)
How To Test for MVD (cont)
How To Test for MVD (cont)
Quick Review of Normal Forms
- 1NF: All values of the attributes contain no repeating values.
- 2NF: 1NF and every non-key attribute is fully dependent upon the primary key.
- 3NF: 2NF and every non-key attribute is functionally dependent only upon the primary key.
- BCNF: 3NF and every determinant (an attribute which some other attribute is fully functionally dependent) is a candidate key.
Fourth Normal Form (4NF)
- Fourth Normal Form (4NF): A relation schema R is in 4NF if there are no non- trivial multi-valued dependencies in R, or the determinant of any non-trivial multi- valued dependency in R is a super key of R. (Informal Definition)