modifying the database structure. objectives examine relational databasesexamine relational...

Modifying the Database Structure

Objectives

• Examine relational databases• Design related tables• Create one-to-many relationships• Create Lookup fields• Modify Short Text fields

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Objectives

• Modify Number and Currency fields• Modify Date/Time fields• Modify validation properties• Create Attachment fields

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Examining Relational Databases

• The purpose of a relational database is to organize and store data in a way that minimizes redundancy and maximizes your flexibility when querying and analyzing data

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Examining Relational Databases

• To redesign a list into a relational database:• Design each table to contain fields that

describe only one subject• Identify a primary key field for each table• Build one-to-many relationships

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Examining Relational Databases

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Designing Related Tables

• After you develop a valid relational database design, you are ready to define the tables in Access.

• Using Table Design View, you can specify all characteristics of a table including field names, data types, field descriptions, field properties, Lookup properties, and primary key field designations.

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Designing Related Tables

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Creating One-to-Many Relationships

• After creating the tables you need, you link them together in appropriate one-to-many relationships using the primary key field in the “one” table and the foreign key field in the “many” table.

• To avoid rework, be sure that your table relationships are finished before building queries, forms, or reports using fields from multiple tables.

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Creating One-to-Many Relationships

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Creating Lookup Fields

• A Lookup field is a field that contains Lookup properties.

• Lookup properties are field properties that supply a drop-down list of values for a field.

• The values can be stored in another table or directly stored in the Row Source Lookup property of the field.

• You can set Lookup properties for a field in Table Design View using the Lookup Wizard.

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Creating Lookup Fields

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Modifying Short Text Fields

• Field properties are the characteristics that describe each field• Field Size• Default Value• Caption• Row Source

• These properties help ensure database accuracy and clarity

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Modifying Short Text Fields

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Common Short Text Field Properties

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Modifying Number and Currency Fields

• Number and Currency fields have similar properties because they both contain numeric values.

• Currency fields store values that represent money, and Number fields store values that represent values such as quantities, measurements, and scores.

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Common Number Field Properties

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Modifying Date/Time Fields

• Many properties of the Date/Time field work the same way as they do in fields with a Short Text or Number data type.

• One difference, however, is the Format property, which helps you format dates in various ways such as January 25, 2013; 25-Jan-13; or 01/25/2013.

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Modifying Validation Properties

• The Validation Rule property determines what entries a field can accept.

• You use the Validation Text property to display an explanatory message when a user tries to enter data that breaks the validation rule.

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Validation Text Message

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Validation Rule Expressions

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Creating Attachment Fields

• An Attachment field allows you to attach an external file to a record.

• The Attachment data type is superior to OLE because it stores data more efficiently, stores more file formats, and requires no additional software to view the files from within Access.

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Creating Attachment Fields

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