Diagnosis and Repair

Appeal to the integrity constraints of a relational database schema

• Integrity constraints can imply regularities in database instances that lead to change anomalies
• Possible repair is to replace a table by two or more other tables

Decomposition

Assume a relation schema is given by a set of Attributes $\{A_1,...,A_k\}$, let $R$ be a relational schema and $\{R_1,\dots ,R_n\}$ be a set of $n$ relational schemata
Then $\{R_1,\dots ,R_n\}$ is a decomposition of $R$ if $$R = \bigcup_{1\leq i\leq n}R_i$$