Saved Bookmarks
| 1. |
What Are Different Normalization Forms? |
|
Answer» 1NF:Eliminate Repeating Groups Make a separate table for each set of related attributes,and give each table a primary key.Each field contains at most one value from its attribute domain. 2NF:Eliminate Redundant DATA If an attribute depends on only part of a multi‐valued key, remove it to a separate table. 3NF:Eliminate Columns Not Dependent On Key If attributes do not contribute to a description of the key, remove them to a separate table. All attributes must be directly dependent on the primary key. BCNF:Boyce‐Codd NORMAL Form If there are non‐trivial dependencies between candidate key attributes,separate them out into distinct tables. 4NF:Isolate Independent Multiple Relationships No table MAY contain two or more 1:n or n:m relationships that are not directly related. 5NF:Isolate Semantically Related Multiple Relationships: There may be practical constrains on information that justify separating logically related many‐to‐many relationships. ONF:Optimal Normal Form A model limited to only simple(elemental) facts,as expressed in Object Role Model NOTATION. 1NF:Eliminate Repeating Groups Make a separate table for each set of related attributes,and give each table a primary key.Each field contains at most one value from its attribute domain. 2NF:Eliminate Redundant Data If an attribute depends on only part of a multi‐valued key, remove it to a separate table. 3NF:Eliminate Columns Not Dependent On Key If attributes do not contribute to a description of the key, remove them to a separate table. All attributes must be directly dependent on the primary key. BCNF:Boyce‐Codd Normal Form If there are non‐trivial dependencies between candidate key attributes,separate them out into distinct tables. 4NF:Isolate Independent Multiple Relationships No table may contain two or more 1:n or n:m relationships that are not directly related. 5NF:Isolate Semantically Related Multiple Relationships: There may be practical constrains on information that justify separating logically related many‐to‐many relationships. ONF:Optimal Normal Form A model limited to only simple(elemental) facts,as expressed in Object Role Model notation. |
|