Best web hosting site - Figure 4-44: 5NF transformations must return records identical
Figure 4-44: 5NF transformations must return records identical to the pre-5NF transformation when joined. Domain Key Normal Form (DKNF) Domain Key Normal Form (DKNF) is quite often a conceptual state of a relational database model as opposed to a final transformation process. DKNF is the ultimate normal form and essentially describes how a completely normalized database model should appear: . There can be no insertion, change, or data removal anomalies. In other words, every record in the database must be directly accessible in all manners, such that no errors can result. . Every record in every table must be uniquely identifiable and directly related to the primary key in its table. This means that every field in every table is directly determined by the primary key in its table. . All validation of data is done within the database model. As far as application and database performance are concerned this is nearly always an extremely undesirable state in a commercial environment. It is better to split functionality between database and applications. Some may call SQL> SELECT project, manager, employee 2 FROM Employee 3 ORDER BY project, manager, employee; PROJECT ———- Analysis Analysis Analysis DW DW DW HTML HTML 8 rows selected. MANAGER ———- Jim Jim Joe Gemima Larry Larry Jackson Jackson EMPLOYEE ———- Magenta Riffraff Brad Columbia Brad Janet Columbia Riffraff SQL> SELECT project, manager, employee 2 FROM Project_Employee 3 NATURAL JOIN Project_Manager 4 NATURAL JOIN Manager_Employee 5 ORDER BY project, manager, employee; PROJECT ———- Analysis Analysis Analysis DW DW DW HTML HTML 8 rows selected. MANAGER ———- Jim Jim Joe Gemima Larry Larry Jackson Jackson EMPLOYEE ———- Magenta Riffraff Brad Columbia Brad Janet Columbia Riffraff Returns identical data and number of rows for both queries Simple query from pre-5th Normal Form transformation table NATURAL JOIN joins on column names regardless of indexes 121 Understanding Normalization
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