Fourth normal form (4NF) is a normal form used in database normalization. Introduced by Ronald Fagin in 1977, 4NF is the next level of normalization after Boyce–Codd normal form (BCNF). Whereas the second, third, and Boyce–Codd normal forms are concerned with functional dependencies, 4NF is concerned with a more general type of dependency known as a multivalued dependency. A Table is in 4NF if and only if, for every one of its non-trivial multivalued dependencies X Y, X is a superkey—that is, X is either a candidate key or a superset thereof.
Read more about Fourth Normal Form: Multivalued Dependencies, Example, 4NF in Practice
Famous quotes containing the words fourth, normal and/or form:
“For the Lord thy God is a jealous God among you.”
—Bible: Hebrew Deuteronomy, 6:15.
The words are also found in Exodus 20:5, referring to the second commandment: “Thou shalt not make unto thee any graven image ... for I the Lord thy God am a jealous God, visiting the iniquity of the fathers upon the children unto the third and fourth generation of them that hate me.”
“When a man says that he is Jesus or Napoleon, or that the Martians are after him, or claims something else that seems outrageous to common sense, he is labeled psychotic and locked up in a madhouse. Freedom of speech is only for normal people.”
—Thomas Szasz (b. 1920)
““Now what I want is, Facts. Teach these boys and girls nothing but Facts. Facts alone are wanted in life. Plant nothing else, and root out everything else. You can only form the minds of reasoning animals upon Facts: nothing else will ever be of service to them.””
—Charles Dickens (1812–1870)