A column (attribute) B is functionally dependent on another column A (or possibly a collection of columns) Show when each value for A in the database is associated with exactly one value of B. The primary key is a column (or a collection of columns) A such that all other columns are functionally depen- dent on A and no subcollection of the columns in A also has this property. When there is more than one choice for the primary key, one of the possibilities is chosen to be the pri- mary key. The others are referred to as candidate keys. A table (relation) is in first normal form (1NF) when it does not contain repeating groups. A column is a nonkey column (also called a nonkey attribute) when it is not a part of the primary key. A table (relation) is in the second normal form (2NF) when it is in first normal form and no nonkey column is dependent on only a portion of the primary key. A determinant is any column that functionally determines another column. A table (relation) is in third normal form (3NF) when it is in second normal form and the only determinants it contains are candidate keys. A collection of tables (relations) that is not in third normal form has inherent problems called update anomalies. Replacing this collection with an equivalent collection of tables (relations) that is in third normal form removes these anomalies. This replacement must be done carefully, following a method like the one proposed in this text. If not, other problems, such as those discussed in this chapter, may be introduced. A table (relation) is in fourth normal form (4NF) when it is in third normal form and there are no multivalued dependencies. alternate key Boyce-Codd normal form (BCNF) candidate key concatenation dependency diagram determinant first normal form (1NF) fourth normal form (4NF) functional dependence functionally dependent functionally determines interrelation constraint multidependent multidetermine multivalued dependence nonkey attribute nonkey column normal form normalization process partial dependency primary key repeating group second normal form (2NF) third normal form (3NF) unnormalized relation update anomaly Define functional dependence. Give an example of a column A and a column B such that B is functionally dependent on A. Give an example of a column C and a column D such that D is not functionally dependent on C. Define first normal form. Define second normal form. What types of problems would you find in tables that are not in second normal form? Define third normal form. What types of problems would you find in tables that are not in third normal form? Define fourth normal form. What types of problems would you find in tables that are not in fourth normal form?  Search WWH :: Custom Search What is a nonkey column?What is a nonkey column? A column that is not part of the primary key.
Is a column in a relation that is neither a primary nor a candidate key column?A nonkey column is a column in a relation that is not a primary or a candidate key column.
Which normal form specifies that nonA relational table is in 3NF if and only if all non-key columns are (a) mutually independent and (b) fully dependent upon the primary key. Mutual independence means that no non-key column is dependent upon any combination of the other columns.
What is a full key functional dependency?A full functional dependency is a state of database normalization that equates to the normalization standard of Second Normal Form (2NF). In brief, this means that it meets the requirements of First Normal Form (1NF), and all non-key attributes are fully functionally dependent on the primary key.
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A nonkey column is a column in a relation that is not a primary or a candidate key column
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