Databases C HAPTER 10. 10 Chapter 10: Databases2 Databases and Structured Fields A database is a...

Databases

CHAPTER 10

Chapter 10: Databases 2

10 Databases and Structured Fields A database is a

collection of information– Typically stored as

computer files

A structured file uses a uniform format to store data in the file


10 Fields

Contain the smallest unit of meaningful information

Each field has a unique field name Variable-length field vs. fixed-length field


10 Records

Collections of data fields

Records can be displayed as rows in a table or as forms.


10 Records

Each kind of record is referred to as a record type


10 Records

A record that contains data is referred to as a record occurrence


10 Relationships and Cardinality

A flat file is a structured file that contains only one record type

A relationship is an association between data that is stored in different record types


10 Relationships and Cardinality

Cardinality refers to the number of associations that can exist between two record types


10 Hierarchical, Network, Relational, and Object-Oriented Databases

A hierarchical databases arranges record types in a hierarchy



The network database model allows many-to-many relationships in addition to one-to-many relationship



A relational database stores data in a collection of related tables



An object-oriented database stores data as objects, which can be grouped into classes and defined by attributes and methods


10 Data Management Software

Microsoft Word allowsyou to create a table ofinformation, such as amailing list, which youcan edit, sort, search,and print. In addition,you can merge data fromthe table with a templateletter to create form letters,mailing labels, andenvelopes.

CLICK TO START



It is possible to enter data as an ASCII text file

Custom data management software Data dependence vs. data independence


10 Database Management Systems



Database client software allows any remote computer or network workstation to access data in a database



Multiple users can interact with the same database


10 Databases and the Web

The Web provides opportunities and challenges for accessing databases– Static Web publishing– Dynamic Web publishing

• Server-side program



Forms can collect data, as well as specifications for a query– XForms



Several tools are available to help create server-side programs


10 XML Documents

Markup language allowing field tags, data, and tables to be incorporated into a Web document


10 XML Documents

Used to specify a standard structure of fields and records

Data in an XML document is searchable XML is portable, but not optimized for many

common database operations– Consider storing data in a relational database,

managing it with RDBMS software, and generating XML documents for exchanging data over the Web


10 Defining Fields

The term database structure refers to the arrangement of fields, tables, and relationships in a database

Store last names and first names in separate fields

Use a primary key field to make each record unique

Use appropriate data types for each field


10 Defining Fields


10 Defining Fields A computed field is a calculation that a DBMS

performs during processing and stores temporarily

Uppercase and lowercase are not always treated the same– Case sensitive database

Use field formats to show what the data is supposed to look like when it’s entered

Use field validation rules to filter data


10 Normalization

Process that helps save storage space and increase processing efficiency– Reduces data redundancy


10 Organizing Records

Records can be organized in different ways, depending on use

Sorting– A table’s sort order refers to the order in which

records are stored on disk– Sort key

Indexing– Similar to the index in a book


10 Organizing Records

When indexed by date, the index file contains a list of keys and the record number (R#)that contains more information about the album released onthat date.


10 Designing the Interface

Arrange fields in a logical order Provide visual clues to the entry areas Entry areas should appear in a consistent

position relative to their labels Provide a quick way to move through the

fields in order



Use scrolling to create multiple screens, if necessary

Provide buttons or other easy-to-use controls for navigating through records

Supply on-screen instructions


10 Designing Report Templates

Report generators are used to specify the content and format for a database report

A report template contains the outline or general specifications for a report


10 Designing Report Templates

Supply only the information required Present information in a usable format Information should be timely Information should be presented in a clear,

unambiguous format Present information in the format most

appropriate for the audience


10 Loading Data

Data can be loaded into a database by:– Using generic data entry tools– Using a customized data entry module

A conversion routine converts the data from its current format into a format that can be automatically incorporated into the new database


10 SQL Basics

Intermediary between the database client software and the database itself


10 SQL Basics


10 Adding Records


10 Searching for Information

SELECT AlbumTitle, AlbumCover FROM Albums

WHERE ArtistName = ‘Jefferson Airplane’

The AND, OR, and NOT Boolean operators are used to perform complex SQL searches

The use of parentheses indicates the part of the query to perform first


10 Updating Fields

UPDATE Albums

SET InStock = InStock – 1

WHERE AlbumTitle = ‘G.I. Blues’

Global updates change the data in multiple records simultaneously– Works only for records with similar characteristics


10 Joining Tables

Joining tables in SQL allows you to create relationships between tables


10 Lab Assignment-Create 3 Database Tables

You are a DBA at Wal-Mart Superstore and you need to create three new database tables for all the items you sell in Excel– Divide the store into 3 sections. Create 1 table

per worksheet for each section. Name the worksheets after each section you create.

– Create all the proper and logical field columns that will be used for each section.

– Fill in the first 3 records for each table with random materials found in that section.

Databases C HAPTER 10. 10 Chapter 10: Databases2 Databases and Structured Fields A database is a...

Documents

Transcript of Databases C HAPTER 10. 10 Chapter 10: Databases2 Databases and Structured Fields A database is a...