Chapter 14Organizing and Manipulating the Data in Databases

• Introduction

• Normalization

• Validating the Data in Databases• Extracting Data From Databases: Data

Manipulation Languages (DMLs)• Object-Oriented Databases, Multimedia

Databases, and Data Warehouses

Normalization

• Flat files are files with no sequence or order to them, except perhaps chronological.

• Flat files make it almost impossible to find a particular record easily or use file data productively.

• Normalization is a process of examining and arranging file data in a way that enables designers to avoid problems when files are used or modified later.

First Normal Form

• A database is in first normal form (1 NF) if all the record’s attributes (data fields) are well defined and the information can thus be stored in a flat file.

• Problems:– data redundancy– insertion anomaly– deletion anomaly

Second Normal Form

• A database is in second normal form (2 NF) if it is in 1 NF and all the data items in each record depend on the record’s primary record key.

• This approach results in a more efficient design and eliminates much of the first file’s data redundancy.

Third Normal Form

• Our goal is to create a database that is minimally in third normal form (3 NF).

• A database is in third normal form if it is in second normal form and contains no transitive dependencies - i.e., no relationships in which data field A determines data field B.

Database Management Systems

• A database management system (DBMS) is a separate software system that enable users to create, delete, access, query, view, analysis, or reorganize modify, and utilize database information more efficiently.

• The data definition language (DDL) of a DBMS enables its users to define the record structure of any particular database table.

• The data manipulation language (DML) enables users to perform tasks such as querying, changing records, and deleting records.

User ViewsSchemas and Subschemas

• The database schema is a map or plan of the entire database.

• Any particular user or application program will be interested in only a subset of the schema, called the subschema.

• A database schema must be flexible enough to satisfy the subschema uses required of it.

Data Manipulation Languages

• Many relational databases support structured query language (SQL).

• Hypertext can also be used for finding information in a database.

• End-user programming allows users to perform their own data processing without technical assistance from IT professionals.

Online Analytical Processing

• Complex multidimensional data analysis performed on database information is called online analytical processing (OLAP).

• OLAP packages allow end users to perform their own database analysis, including data mining.

Object-Oriented and Multimedia Databases

• The object-oriented database (OODB) contains both the text data of traditional databases and information about the set of actions that can be taken on these data fields.

• Many OODBs are multimedia databases that include graphics, audio information, and animation.

Characteristics of a Data Warehouse

• A data warehouse pools data from separate applications into a large common body of information. Characteristics of data warehouses:1. Data are free of errors.2. Defined uniformly.3. Span a longer time horizon than the

company’s transaction systems.4. Optimized data relationships that allow

user to answer complex questions.

Advantages ofData Warehouse

• Make organizational information available on a corporate-wide basis, which is central to the concept of enterprise-wide databases.

• Facilitates data mining and enables users to identify target markets or its most desirable customers.

Copyright

Copyright 2007 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in Section 117 of the 1976 United States Copyright Act without theexpress written permission of the copyright owner is unlawful. Request for further information should be addressed to the Permissions Department, John Wiley & Sons, Inc. The purchaser may make backup copies for his/her own use only and not for distributionor resale. The Publisher assumes no responsibility for errors, omissions, or damages, caused by the use of these programs or from the use of the information contained herein.

Chapter 14