First normal form (1NF) is the same as the definition of relational model (relations = sets of tuples; each tuple = sequence of atomic values) Boyce-Codd Normal Form A simple condition for removing anomalies from relations: A relation R is in BCNF if and only if: Whenever there is a nontrivial dependency for R, it is the case that { } a super-key for R. A,A, An A,A, A Bn In English (though a bit vague): Whenever a set of attributes ofR is determining another attribute Boyce-Codd Normal Form. Into “good” relations Each normal form is a set of conditions on a schema that together guarantee certain properties (relating to redundancy and update anomalies). Example Relational design by omposition. “Good” ompositions only. System Boyce-Codd Normal Form. Relational design by omposition. Definition (Boyce-Codd Normal Form) A relation R is in Boyce-Codd normal form (BCNF) if for every nontrivial functional dependency X! A, X is a When a database schema is un-normalized (that is, does not satisfy the normal form), it allows redundancies of various types which can lead to anomalies and inconsistencies Boyce-Codd Normal Form A simple condition for removing anomalies from relations: A relation R is in BCNF if and only if: Whenever there is a nontrivial dependency for R, it Introduction to Databases. Example: Person1(Person1 SI#, Name, Address) 9The only FD is SI# →Name, Address Boyce-Codd Normal Form. System omposes based on properties. That is, Y is a superkey for R(X). We say a relation R is in BCNF if whenever X → Y is a nontrivial FD that holds in R, X is a superkey. “Mega” relations + properties of the data. Boyce-Codd Normal Form. “Mega” relations + properties of the data. Relational Design Theory. Remember: nontrivial contained in X CSC – Introduction to Databases Normal Forms —Boyce–Codd Normal Form (BCNF) A relation R(X) is in Boyce–Codd Normal Form if for every non-trivial functional dependency Y →Z defined on it, Y contains a key K of R(X). Definition (Boyce-Codd Normal Form) A relation R is in Boyce-Codd normal form (BCNF) if for every nontrivial functional dependency X! A, X is a superkey of R. That is, no attribute (prime or nonprime) depends on anything less than a superkey.
First normal form (1NF) is the same as the definition of relational model (relations = sets of tuples; each tuple = sequence of atomic values) Boyce-Codd Normal Form A simple condition for removing anomalies from relations: A relation R is in BCNF if and only if: Whenever there is a nontrivial dependency for R, it is the case that { } a super-key for R. A,A, An A,A, A Bn In English (though a bit vague): Whenever a set of attributes ofR is determining another attribute Boyce-Codd Normal Form. Into “good” relations Each normal form is a set of conditions on a schema that together guarantee certain properties (relating to redundancy and update anomalies). Example Relational design by omposition. “Good” ompositions only. System Boyce-Codd Normal Form. Relational design by omposition. Definition (Boyce-Codd Normal Form) A relation R is in Boyce-Codd normal form (BCNF) if for every nontrivial functional dependency X! A, X is a When a database schema is un-normalized (that is, does not satisfy the normal form), it allows redundancies of various types which can lead to anomalies and inconsistencies Boyce-Codd Normal Form A simple condition for removing anomalies from relations: A relation R is in BCNF if and only if: Whenever there is a nontrivial dependency for R, it Introduction to Databases. Example: Person1(Person1 SI#, Name, Address) 9The only FD is SI# →Name, Address Boyce-Codd Normal Form. System omposes based on properties. That is, Y is a superkey for R(X). We say a relation R is in BCNF if whenever X → Y is a nontrivial FD that holds in R, X is a superkey. “Mega” relations + properties of the data. Boyce-Codd Normal Form. “Mega” relations + properties of the data. Relational Design Theory. Remember: nontrivial contained in X CSC – Introduction to Databases Normal Forms —Boyce–Codd Normal Form (BCNF) A relation R(X) is in Boyce–Codd Normal Form if for every non-trivial functional dependency Y →Z defined on it, Y contains a key K of R(X). Definition (Boyce-Codd Normal Form) A relation R is in Boyce-Codd normal form (BCNF) if for every nontrivial functional dependency X! A, X is a superkey of R. That is, no attribute (prime or nonprime) depends on anything less than a superkey.
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