CHAPTER EIGHT

Accessing Data

Processing Databases

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Introduction

• Data is efficiently managed by storing them in files on disk.

• Data files and programs are separate.• The program does not need to be modified when

the data changes.• Different programs can share the same data

sets.

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Introduction (cont.)

• Most businesses organize their data into databases.

• A database is an organizes collection of data.• A database management system (DBMS) is a

program that is used to create and maintain databases.

• Visual Basic .NET provides tools for developers to access databases from their programs.

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Objectives

• Understand and use relational databases.• Understand a subset of the ADO.NET object

model.• Apply the ADO.NET object model within Visual

Basic .NET to access databases.• Use the properties and methods of the DataGrid

control to display record from a DataSet.

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Objectives (cont.)

• Write SQL Select queries to extract data from a database.

• Bind controls such as TextBoxes and Labels to a DataSet.

• Create Master/Detail DataSets.• Use several tools within Visual Basic .NET to

manage and use databases.

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8.1 A Relational Database Primer

• Entities and Relationships– Every database contains:

• Entities – anything of interest to a business.• Relationships – real-world associations between

entities.

– Database developers often use an entity-relationship diagram (ERD).

• To document a database’s structure.• Symbols are used to designate relationships

between entities.

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8.1 A Relational Database Primer (cont.)

• Relational Database Tables– A relational database stores the data for each

entity in a table with rows and columns.

– Compatible with Visual Basic .NET.

– A key field guarantees the uniqueness of records.

– A combination key is a key field with a combination of two or more fields.

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8.1 A Relational Database Primer (cont.)

– One-to-Many Relationships• Established by placing the key field of the “one”

entity’s table into the “many” entity’s table as a foreign key.

– Many-to-Many Relationships• Constructed by creating a new table with the key

fields from related tables.

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8.1 A Relational Database Primer (cont.)

– Normalized Databases• Normalization is a process used to eliminate or

reduce data redundancy.• Designers must determine which tables to place

information in.• A table should be in third normal form.

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8.1 A Relational Database Primer (cont.)

• Database Queries– Most relational database systems use a query

language called structured query language (SQL).

• To specify how to combine data in related tables.• To specify how to select only the desired data.

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8.2 An Introduction to ADO.NET

• Visual Basic .NET uses ADO.NET to manage data in a database.– ADO.NET (ActiveX Data Objects) uses an

extensive set of classes to manage data.

– This chapter covers the foundations of ADO.NET.

– Also we will cover some of the wizards and tools provided to work with relational databases.

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8.2 An Introduction to ADO.NET (cont.)

• An Overview of ADO.NET– A DataProvider object directly interacts with a

database and its DBMS.

– A Connection object makes the physical connection to the database.

– A DataSet class holds the actual data.

– User interface components work directly with the DataSet.

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8.3 Using ADO.NET with Visual Basic .NET

• Data Access Using the DataGrid Control– Provides a method of displaying records from a

database in a grid-like manner.

– Building the DataAdapter• Create a DataAdapter by a wizard.

– Building the DataSet• Follow the procedure to create a DataSet.

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8.3 Using ADO.NET with Visual Basic .NET (cont.)

– Adding the DataGrid• Follow the procedure to add a DataGrid to the

form.• Set the DataGrid properties to connect it to the

DataAdapter and DataSet.• Found on the Windows Form tab in the Toolbox.• Will display fields specified in the SQL Select

statement.

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8- 158.3 Using ADO.NET with Visual Basic .NET

(cont.)

• The DataGrid Control– Designed to display the data stored in a DataSet.

– An expander allows navigation from a parent table to a child table.

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8- 168.3 Using ADO.NET with Visual Basic .NET

(cont.)

– PropertiesAllowSorting CurrentCell

AlternatingBackColor CurrentRowIndex

BackColor DataMember

BackgroundColor DataSource

BorderStyle Enabled

CaptionBackColor FirstVisibleColumn

CaptionFont ForeColor

CaptionForeColor GridLineColor

CaptionText GridLineStyle

CaptionVisible HeaderBackColor

ColumnHeadersVisible HeaderFont

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8- 178.3 Using ADO.NET with Visual Basic .NET

(cont.)

– Properties (cont.)HeaderForeColor

ParentRowsBackColor

ParentRowsForeColor

ParentRowsVisible

PreferredColumnWidth

ReadOnly

RowHeadersVisible

RowHeaderWidth

SelectionBackColor

SelectionForeColor

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8- 188.3 Using ADO.NET with Visual Basic .NET

(cont.)

– Methods• Collapse(row)• Expand(row)• IsExpanded(row)• IsSelected(row)• Select(row)• SetDataBinding(dataSourceObject,

dataMemberString)• UnSelect(row)

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8- 198.3 Using ADO.NET with Visual Basic .NET

(cont.)

• Updating a Table– ADO.NET provides support for table update.

– Changes in the DataGrid can be relayed back to the original source data.

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8- 208.3 Using ADO.NET with Visual Basic .NET

(cont.)

• Parameterized Queries– Users will often want to specify information that

will determine the results of a query.

– A parameter of a query could be a zipcode.

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8- 218.3 Using ADO.NET with Visual Basic .NET

(cont.)

• Master/Detail Record Display– Here we examine a DataSet that includes two

tables related to a common field.

– A master/detail DataSet is a dataset with more than one table.

– Each master record is related to zero or more records from the second table.

– Parent and child terms may refer to master and detail records.

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Tools

• We look at using the Server to work with databases.

• We show how to add a data connection to the server.

• The data connection will be used to create a data adapter and data set.

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Chapter Summary

• A database is an organized collection of data and relationships that describe entities of interest to a business.

• An entity-relationship diagram (ERD) documents entities and their relationships.

• Visual Basic .NET supports the relational database approach for organizing data.

• Normalization is process used to minimize data redundancy.

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Chapter Summary (cont.)

• Visual Basic .NET uses ADO.NET to access and manage databases.

• The DataGrid control is a control that can be bound to a specific dataset.

• Parameterized queries provide for the ability to determine how records will be selected at run time.

• Many of Visual Basic .NET’s controls can be bound to a dataset and its fields.

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Chapter Summary (cont.)

• ADO.NET supports master/detail record relationships.

• The Server Explorer provides access and management tools for connections and servers.