Chapter 16 (p481 – 485, 496-501) Fluency with Information Technology 4 th edition by Lawrence...

Chapter 16 (p481 – 485, 496-501)

Fluency with Information Technology4th edition

by Lawrence Snyder(slides by Deborah Woodall : [email protected])

1

Database Defined

database – an organized collection of related information, used primarily to maintain and look up that information.

relational database -the most common type of database

•Data is organized into tables that have rows and columns.•Thus, a database is a collection of one or more tables

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Part of a Database Table called Nations

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Nations

Name Domain Capital Latitude N_S Longitude E_W Interest

Australia AU Canberra 37 S 148 E Beach

Bahamas BS Nassau 25 N 78 W Beach

Barbados BB Bridgetown 13 N 59 W Beach

Belize BZ Belize 17 N 18 W Beach

Bermuda BM Hamilton 32 N 64 W Beach

Cyprus CY Nicosia 35 N 32 E History

Czech Rep. CZ Prague 51 N 15 E Pilsner

Denmark DK Copenhagen 55 N 12 E History

Falkland IS. FK Stanley 51 S 58 W Nature

Finland FI Helsinki 64 N 26 E Nature

Greenland GL Nuuk 72 N 40 W Nature

Iceland IS Reykjavik 65 N 18 W Geysers

Ireland IE Dublin 52 N 7 W History

13 Rows, Tuples, Records

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Nations















8 Columns, Fields, Attributes

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NationsName Domain Capital Latitude N_S Longitude E_W Interest




Belize BZ Belize 17 N 18 W BeachBermuda BM Hamilton 32 N 64 W Beach









Properties of Database Tables

• A relational database table can be empty.

• Two tables with the same rows, but in a different order, are the same table.

• Two tables with the same columns, but in a different order, are the same table.

• Thus the information in a database can be ordered (i.e. sorted) in any order that you need.

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Properties of Database Tables: An Empty table

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Nations


Properties of Database Tables:Two views of the same table

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NationsName Domain Capital Latitude N_S Longitude E_W InterestAustralia AU Canberra 37 S 148 E BeachBahamas BS Nassau 25 N 78 W BeachBarbados BB Bridgetown 13 N 59 W BeachBelize BZ Belize 17 N 18 W BeachBermuda BM Hamilton 32 N 64 W BeachCyprus CY Nicosia 35 N 32 E History

Nations









• Every row of a database table must be unique in some way.

• The field (i.e. column or attribute) for which all rows of the data base table are unique is the primary key of the table.

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A Database Table called Nations

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Nations
















• Field names (i.e. column names, attribute names) should be descriptive.

• Attribute data (i.e. column data, field data) is atomic – Or Indivisible– The value of a field (i.e. column, attribute) can not

be subdivided into several smaller parts– The date attribute is a classic exception

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A Database Table called Nations

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Nations















Database Scheme

• Also called database schema

• It is the collection of all table definitions for a database.

• Each table definition includes– Table name– Fields with data types– Primary key indicated

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A Table Definition for Nations Table

• Name: Nations• Fields: (with data type and primary key indicated)

Name (Text)Domain (Text)Capital (Text)Latitude (Text)N_S (Number)Longitude (Text)E_W (Number)Interest (Text)

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Physical Database

The physical database

• It is made up of all of the physical tables.

• Major rule: No Redundancy!

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Nations is a Physical Table

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Nations















Logical Database and Queries

• It is made up of all of the logical tables.• A logical table is created as the result of a

query.• A query is an operation on one or more

database tables that pulls info from the database.

• For complex queries, go beyond "drag and drop" with Structured Query Language (SQL)

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Query 1 us a Logical Table

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Query1

Name Domain

Bahamas BS

Barbados BB

Belize BZ

Bermuda BM

Created by a Query on the Nations Table

Creating Queries (i.e. logical tables)

Steps to create each query…1.Select the table or tables with the needed

data2.Select the fields you wish to see3.Set the criteria for which rows you want4.Sort as prescribed

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Entity Relationship diagrams

• Also called ER diagrams

• Show the relationships between the physical tables in the physical database.

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ER Diagram

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ER Diagram: ∞ to 1

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Chapter 16 (p481 – 485, 496-501) Fluency with Information Technology 4 th edition by Lawrence...

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