Design of Relational Database Schemas / Anomalies

Careless selection of a relational database schema can lead to problems. For instance, Example (b) of "Combining Relations" showed what happens if we try to combine the relation for a many-many relationship with the relation for one of its entity sets. The major problem we

Decomposing Relations

The accepted way to remove these anomalies is to decompose relations. Decomposition of R involves splitting the attributes of R to make schemas of two new relations. Our decomposition rule also includes a way of populating those relations with tuples by "projecting" the tuples


The fact that movies like Star Wars will appear in various relations that are values of the movies attribute in the nested relation Stars is a cause of redundancy. In effect, the schema of Nested Relations Example (a) has the nested-relation analog of not being in BCNF. On the

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