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| -rw-r--r-- | doc/01-introduction.md | 8 |
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diff --git a/doc/01-introduction.md b/doc/01-introduction.md index ce9db0d..23184c1 100644 --- a/doc/01-introduction.md +++ b/doc/01-introduction.md @@ -47,6 +47,7 @@ Employee1(id, name) # shorthand notation for describing a relation. * primary key: attribute or combination of attributes that uniquely identifies each row in a relation. * composite key: primary key that consists of more than one attribute. * foreign key: attribute in a relation that serves as the primary key of another relation in the same db. +* enterprise key: A primary key whose value is unique across all relations. Not all tables are relations. @@ -150,3 +151,10 @@ A normal form is a state of a relation that requires that certain rules regardin * Boyce-Codd normal form: remaining anomalies from functional dependencies have been removed. * 4th normal form: multivalued dependencies have been removed. * 5th normal form: remaining anomalies have been removed. + +> functional dependency: a constraint between two attributes in which the value of one attribute is determined by the value of another attribute. + + +* Synonyms: Two (or more) attributes that have different names but the same meaning. +* Alias: An alternative name used for an attribute. +* Homonym: An attribute that may have more than one meaning. |