8 - Functional Dependencies & Normalization (Lecture...

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Functional Dependencies Normalization (Lecture Session-9) Mon, Feb 08, 2010 1 DLPD, BITS-Pilani. Prepared by Dr.R. Gururaj, Asst.Professor of CS
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Mon, Feb 08, 2010 DLPD, BITS-Pilani. Prepared by Dr.R. Gururaj, Asst.Professor of CS 2 •Functional Dependencies •Normalization •Normal forms •Decompositions Contents
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Mon, Feb 08, 2010 DLPD, BITS-Pilani. Prepared by Dr.R. Gururaj, Asst.Professor of CS 3 All database applications have certain constraints that must hold for the data. A DBMS must provide capabilities for defining and enforcing these constraints. These set of constraints help to make the system to accept correct and valid data. Types of Integrity Constraints Domain constraints – Data type, Null, Check for certain range. Entity constraints – Primary key and Unique key Referential integrity – Foreign key
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Mon, Feb 08, 2010 DLPD, BITS-Pilani. Prepared by Dr.R. Gururaj, Asst.Professor of CS 4 Database Design A good database design practice is essential to develop good relational schemers at logical and implementation level. Good database design is needed for: Clarity in understanding the database and To formulate good queries Informal Design Guidelines Semantics of the attributes must be meaningful. Data redundancy must be avoided to avoid insert/update/deletion anomalies. As far as possible avoid placing attributes in a base relation whose values may frequently be null. Design relations such that they can be joined with equality condition on attributes that are PK or FK that guarantees no spurious tuples in the result.
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Mon, Feb 08, 2010 DLPD, BITS-Pilani. Prepared by Dr.R. Gururaj, Asst.Professor of CS 5 Functional Dependencies It is a constraint between two sets of attributes from the database. If a relational database schema has n attributes A 1 , A 2 , A 3 ,…. ., A n , then think of it as a universal database schema R = {A 1 , A 2 , A 3 ,……A 4 }. This is not a real table, this is conceptual for developing formal theory of data dependencies. Function Dependency Denoted by X Y between two sets of attributes in R, and specifies a constraint on the possible tuples that can form a relational state r of R. Values of Y component are determined by X component. (or) Y is functionally dependent on X.
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This note was uploaded on 03/14/2010 for the course CSE IS ZC332 taught by Professor Shailendrasshekhawat during the Summer '10 term at Birla Institute of Technology & Science.

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8 - Functional Dependencies & Normalization (Lecture...

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