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Web-Enabled Decision Support Systems Advance Topics in Database Connectivity

Prof. Name Position University Name 1 [email protected]

(123) 456-7890

Overview

           

15.1 Introduction

15.2 ADO .NET Architecture 15.3 A Database Connection 15.4 Hands-On Tutorial: Displaying Data with Multiple Parameters 15.5 Hands-On Tutorial: Displaying Data from Join of Tables 15.6 Hands-On Tutorial: Displaying Data Using Access Query 15.7 Hands-On Tutorial: Passing Data between Forms 15.8 DataSets 15.9 Inserts, Updates, and Deletes in a Windows Application 15.10 Hands-On Tutorial: Updating Changes to Multiple Tables 15.11 In-Class Assignment 15.12 Summary 2

Introduction

 In the previous chapter, we discussed basic database connectivity topics: – The Data Sources Window – Displaying information on Windows forms – Displaying data from related tables – Building search forms and look-up tables  Real life database applications are seldom so simple – Fortunately, Visual Studio provides a rich set of tools to develop professional applications efficiently – In this chapter, we will study advanced database connectivity topics 3

Overview

            15.1 Introduction

15.2 ADO .NET Architecture

15.3 A Database Connection 15.4 Hands-On Tutorial: Displaying Data with Multiple Parameters 15.5 Hands-On Tutorial: Displaying Data from Join of Tables 15.6 Hands-On Tutorial: Displaying Data Using Access Query 15.7 Hands-On Tutorial: Passing Data between Forms 15.8 DataSets 15.9 Inserts, Updates, and Deletes in a Windows Application 15.10 Hands-On Tutorial: Updating Changes to Multiple Tables 15.11 In-Class Assignment 15.12 Summary 4

ADO .NET Architecture

 ActiveX Data Objects (ADO) .NET is the collection of objects that are designed to support data access and data manipulation  Database connectivity involves the following entities: – Database  Stores data on the hard drive (disk) – Connection  Connects to the database – DataAdapter  Hosts SQL queries and executes them against the database – DataSet  Stores data in main memory – Form  Displays data to the user 5

ADO .NET Architecture

(cont.)  From database to Windows forms: 1. A

Connection

object opens a live connection to the database 2. A

DataAdapter

object executes Select SQL queries against the database 3. The

DataAdapter

object further

fills

 a

DataSet

object with query results The

DataSet

stores the results in the main memory

4. DataSets

are associated with various Windows controls on a form  This association is referred to as

Data Binding

 Data binding makes it possible for the query results in the

DataSet

to be displayed on a form for the user ADO .NET Architecture 6

ADO .NET Architecture

(cont.)  From Windows forms to database: 1. If a user edits the data in Windows controls, the updates are propagated to the

DataSet

object 2. The

DataAdapter

object then propagates the updates from the

DataSet

object to the connected database by executing Update SQL statements 7

Overview

            15.1 Introduction 15.2 ADO .NET Architecture

15.3 A Database Connection

15.4 Hands-On Tutorial: Displaying Data with Multiple Parameters 15.5 Hands-On Tutorial: Displaying Data from Join of Tables 15.6 Hands-On Tutorial: Displaying Data Using Access Query 15.7 Hands-On Tutorial: Passing Data between Forms 15.8 DataSets 15.9 Inserts, Updates, and Deletes in a Windows Application 15.10 Hands-On Tutorial: Updating Changes to Multiple Tables 15.11 In-Class Assignment 15.12 Summary 8

A Database Connection

 Creating a

database connection

is like opening a unique session with the database – We can access contents of the database using the connection object – There are two ways to create a database connection in Visual Studio:   Using the

Data Source Configuration

wizard Using the Server Explorer Window 9

Creating the Project and Data Connection

 How-to: Create a Connection Using the Server Explorer Window 1. Create a new Windows Application with the name,

AdvanceDBConnectivity

. 2. Select the

View

Server Explorer

Server Explorer Window. option from the Main menu to open the 3. Right-click the

Data Connection Connection

option.

node in the window and choose the

Add

Adding a Connection in the Server Explorer Window 10

Creating the Project and Data Connection

(cont.) 4. If the

Choose Data Source

dialog box opens, select the

Microsoft Access Database File

option and click

Continue

. Otherwise, we should directly see the

Add Connection

dialog box. Select the University database. Test the connection and click

The

Add Connection

Dialog Box 11

Creating the Project and Data Connection

(cont.) 5. Collapse the

Tables

node and

Views

queries from the University database.

node to explore the list of tables and Server Explorer Window for University Database 12

Creating the Data Source

6. Choose the

Data

Show Data Sources

option from the Main menu.

7. In the Data Sources Window, click

Add New Data Source

to start the

Data Source Configuration

wizard.

8. Select the

Database

icon on the

Choose a Data Source Type

click

Next

page, and then 9. On the

Choose Your Data Connection

page, accept the University database connection we have created in the previous step and click

Next

Accepting Connection Created in the Server Explorer Window 13

Creating the Data Source

(cont.) 10. When enquired, copy the database to the current project folder. Click

Next

11. On the next page of the wizard save the connection with the default name

UniversityConnectionString

. Click

Next

12. Expand the

Tables

node on the

Choose Your Database Objects

page, and select all the tables except the college table and click

Finish

. The Data Sources Window now displays the

UniversityDataSet

tables.

Selecting Tables for a Data Source 14 Data Sources Window

Properties of a Connection Object

 There are several important properties related to

Connection

objects: –

Name:

 The name given to a

Connection

object –

Connection String:

 The string that stores the information required to connect to the database  A typical

ConnectionString

property resembles the following string: Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\University.mdb –

Provider:

 Shows the type of the database 

Jet Engine

for MS Access database –

Data Source:

 Stores the physical path of the database file 15

Methods of a Connection Object

 There are two primary methods available for

Connection

objects: –

Open:

 This method makes use of the information in the

ConnectionString

to locate the database and open a unique session to work with it –

Close:

 This method shuts the connection down.

 Closing connections is essential because most databases support only a limited number of open connections  We use a

TableAdapter

to maintain the

Connection

object – Opens and closes the connection as per the applications need – Makes application development easier, faster, and less error-prone 16

Overview

            15.1 Introduction 15.2 ADO .NET Architecture 15.3 A Database Connection

15.4 Hands-On Tutorial: Displaying Data with Multiple Parameters

15.5 Hands-On Tutorial: Displaying Data from Join of Tables 15.6 Hands-On Tutorial: Displaying Data Using Access Query 15.7 Hands-On Tutorial: Passing Data between Forms 15.8 DataSets 15.9 Inserts, Updates, and Deletes in a Windows Application 15.10 Hands-On Tutorial: Updating Changes to Multiple Tables 15.11 In-Class Assignment 15.12 Summary 17

Create a DataGridView Control

 This application will be based on the faculty table – The two parameters are the faculty’s department and salary, which are input by the user – We display the faculty members who belong to the user-specified department and whose salary is at least as much as specified by the user  How-to: Display Data on a Form with Multiple Parameters 1. In the Data Sources Window, locate and drag the faculty table onto

Form1

. This creates:    The data bound

DataGridView

control A

ToolStrip

control Related objects in the Component tray 18

Open the DataSet Designer

2. Right-click

TblFacultyTableAdapter

from the Component tray and choose

Edit Queries in DataSet Designer

option to open the

DataSet Designer

tab.

Invoking the

DataSet Designer

to Edit Queries – Alternatively:  Double-click the

DataSet

(.xsd) file from the Solution Explorer Window  Click the

Edit DataSet with Designer

icon from the Data Sources Window Opening the

DataSet Designer

Adding Parameter Queries

3. Select the

TblFacultyTableAdapter

in the

DataSet Designer,

right click “

Fill, GetData ()

” text, and choose the

Configure

option. This should open the

TableAdapter Configuration

wizard.

Review and Configure Existing Queries in a

TableAdapter

Adding Parameter Queries

(cont.) – In the

TableAdapter Configuration

wizard, we have the Select query based on the faculty table.  We can modify the existing query by either editing the SQL statement or using the

Query Builder

dialog box. Edit Existing Query Using

TableAdapter Configuration

Wizard 21

Adding Parameter Queries

(cont.) 4. Select the

TblFacultyTableAdapter

in the

DataSet Designer

and right-click to choose the

Add Query

option to open the

Query Configuration

wizard.

Adding a Query to a

TableAdapter

4. On the first page of the wizard (

Choose a Command Type

), choose the

Use SQL statements

option and click

Next

Choosing a Command Type 22

Adding Parameter Queries

(cont.) 6. On the next page (

Choose a Query Type

), choose the first option (

SELECT which returns rows

) and click

Next.

Choosing the Query Type in

TableAdapter Query Configuration

Wizard 23

Adding Parameter Queries

(cont.) 7. On the next page (

Specify a SQL SELECT statement

), create a new query by entering the SQL statement on this page.

Writing a SQL Query in

TableAdapter Query Configuration

Wizard 24

Adding Parameter Queries

(cont.) 8. Finally, name the

Fill a DataTable

shown in below and click

Finish

and

Return a DataTable

methods as Choose and Name the Methods to be Added to the

TableAdapter

– The faculty

TableAdapter

now resembles below with its additional methods. Faculty

TableAdapter

with Parameterized Query 25

Add Existing Query

9. Right-click the

TblFacultyTableAdapter

from the Component tray and choose the

Add Query

option to open the

Search Criteria Builder

dialog box.

10. Choose the

Existing query name

option. Then, choose the

FillByDeptSal

method we created in the previous step from the drop-down list. Assigning a Query to a

TableAdapter

in the

Search Criteria Builder

Dialog Box 11. Click

to create two

TextBox

controls for user input in the

ToolStrip

Test the Application

12. Press

Ctrl

to run and test the application.  Enter values for the department and salary parameters through the

TextBox

controls on the

ToolStrip

and check if all the records satisfy the specified criteria. Running Application with Two Input Parameters 27

Code Review

 Note the code used to assign multiple parameters (lines 21-25).

Code Review for the Multiple Parameter Query 28

Overview

            15.1 Introduction 15.2 ADO .NET Architecture 15.3 A Database Connection 15.4 Hands-On Tutorial: Displaying Data with Multiple Parameters

15.5 Hands-On Tutorial: Displaying Data from Join of Tables

15.6 Hands-On Tutorial: Displaying Data Using Access Query 15.7 Hands-On Tutorial: Passing Data between Forms 15.8 DataSets 15.9 Inserts, Updates, and Deletes in a Windows Application 15.10 Hands-On Tutorial: Updating Changes to Multiple Tables 15.11 In-Class Assignment 15.12 Summary 29

Add a New TableAdapter

 How-to: Display Data on a Form from a Join of Multiple Tables 1. Add a new form,

Form2

, to the

AdvanceDBConnectivity

application.

2. Open the

DataSet Designer

. Right-click anywhere in the designer window and choose the

Add

TableAdapter

option to open the

TableAdapter Configuration

wizard.

Adding a New

TableAdapter

to the Application 30

Add a New TableAdapter

(cont.) 3. On the

Choose Your Data Connection

page, accept the selected University database connection string. Click Next.

Specifying Connection for a New

TableAdapter

4. On the

Choose a Command Type

page, check

Use SQL statements

(default) and click

Next

option 31

Add a New TableAdapter

(cont.) 5. On the

Enter a SQL Statement Add Table

click

Add

page, click on the

QueryBuilder

button. In the dialog box that opens, select the student and transcript tables and Adding Query Tables in the

Query Builder

Dialog Box 32

Add a New TableAdapter

(cont.) 6. Note that the two selected tables appear in the table pane of the

Query Builder

dialog box. Click

Close

on the

Add Table

dialog box.

Query Builder

Dialog Box Showing the Query Design 33

Add a New TableAdapter

(cont.) 7. Select the fields to be displayed from the student and transcript tables (

StudentID

DeptID

, and

Name

from student table and

Grade

transcript table). field from the  Notice that the corresponding SQL Select query (performing the join of the two tables) is automatically built in the SQL pane as we select the fields.

8. Now add the DISTINCT keyword after the SELECT keyword in the SQL pane.

9. Add the query parameters (

DeptID

and

Grade

) in the WHERE clause. 34

Add a New TableAdapter

(cont.) 10. Click

on the

Query Builder

dialog box. Click

Next

on the

Table Adapter Configuration

wizard, accept the default method names

Fill

and click

Finish

. and

GetData

, Newly Added

TableAdapter

in the

DataSet

Designer Newly Added

DataTable

in the Data Sources Window 35

Create a DataGridView Control and Test

11. From the Data Sources Window, drag-and-drop the

DataTable1

table on

Form2

to create a

DataGridView

control. 12. Set

Form2

as the start-up object. Press

Ctrl

to run the application. Test the application by entering different department IDs through the

ToolStrip.

Data from the Join of Two Tables 36

Overview

15.6 Hands-On Tutorial: Displaying Data Using Access Query

15.7 Hands-On Tutorial: Passing Data between Forms 15.8 DataSets 15.9 Inserts, Updates, and Deletes in a Windows Application 15.10 Hands-On Tutorial: Updating Changes to Multiple Tables 15.11 In-Class Assignment 15.12 Summary 37

Add Access Query

 How-to: Display Data Using Existing MS Access Query 1. Add a

Form3

to the

AdvanceDBConnectivity

application.

2. In the Data Sources Window, click the

Configure DataSet with Wizard

open the

Choose DataSet Editor

dialog box.

icon to Using Data Sources Window to Invoke the

Dataset Configuration

Wizard 38

Add Access Query

(cont.) 3. Choose the

Continue with wizard

option to open the

Data Source Configuration

wizard.

Invoking

Data Sources Configuration

Wizard 39

Add Access Query

(cont.) 4. On the last page of the wizard,

Choose Your Database Objects

, collapse the

Views

node and choose a

DataTable qryGPA

, and click in the Data Sources Window.

Finish

. This adds the

qryGPA

as Choosing the Query 40 Access Query as a

DataTable

in the Data Sources Window

Create a DataGridView and Test

5. From the Data Sources Window, drag-and-drop the

qryGPA

data table on

Form3

to create a

DataGridView

control. 6. Set

Form3

as the start-up object. Press

Ctrl

to run the application. Navigate through the student records and notice that the calculated GPA is displayed in column 5.

Running Application with Student GPAs 41

Overview

15.7 Hands-On Tutorial: Passing Data between Forms

15.8 DataSets 15.9 Inserts, Updates, and Deletes in a Windows Application 15.10 Hands-On Tutorial: Updating Changes to Multiple Tables 15.11 In-Class Assignment 15.12 Summary 42

Passing Data Between Forms

Application Flow: Passing Data between Two Windows Forms 43

Create the First (Faculty) Form

 How-to: Pass Data between Two Windows Forms 1. Add

Form4

to the

AdvanceDBConnectivity

application.

2. Drag-and-drop the faculty table from the Data Sources Window on

Form4

.  This should create the faculty

DataGridView

and related objects in the Component tray.

Create the Second (Course) Form

3. Add

Form5

to the same application.

4. Switch to the

DataSet Designer

by double-clicking on

UniversityDataSet.xsd.

5. Right-click in the designer window to add a new

TableAdapter.

6. Follow the

TableAdapter Configuration

wizard as described in the previous hands-on tutorial. On the

Enter a SQL Statement

page of the wizard, click on the

Query Builder

button and add

tblSection

and

tblCourse

tables to the query design. Design the SQL statement shown below using the

Query Builder

dialog box.

Course Information Query for the Course Form 45

Create the Second (Course) Form

(cont.) 7. Rename the

Fill

method as

FillFaculty

wizard.

before finishing the configuration 8. Name the new table adapter as

qryFacultyCoursesTableAdapter

new data table as

qryFacultyCourses

and the 9. Drag-and-drop the

qryFacultyCourses

Window on

Form5

.  data table from the Data Sources This should create the courses DataGridView and related objects in the Component tray.

Write a Subroutine

10. In the

Form5.vb

file, write a new subroutine

LoadCourses

 as shown below.

Takes in the

FacultyID

as an argument and passes it as a parameter to the

FillFaculty

method. Subroutine to Load Course Information for a Given

FacultyID

Write Code to Handle Events

11. In the faculty form,

Form4.vb

, write the code for

DataGridView’s DoubleClick

event. Select the

TblFacultyDataGridView DoubleClick

from the left drop-down list and its event from the right drop-down list at the top of the Code Window. Associate the code below with this event.

DoubleClick

Event of a

DataGridView

for the Faculty Form 48

Test the Application

12. Set

Form4

as the application’s start-up object. Press

Ctrl

to run the application. Test the application by double-clicking any faculty record from the

DataGridView

and viewing the related course data.

Running Application Showing Related Information 49

Overview

15.8 DataSets

15.9 Inserts, Updates, and Deletes in a Windows Application 15.10 Hands-On Tutorial: Updating Changes to Multiple Tables 15.11 In-Class Assignment 15.12 Summary 50

DataSets

 A

DataSet

is an in-memory relational database – As relational databases have tables,

DataSets

also have

DataTables

– As database tables have rows and columns,

dataset’s DataTables DataRows

and

DataColumns

also have – As database tables are related to each other through relationships,

DataTables

are linked together through

DataRelations

object The Architecture of a

DataSet

Object 51

How-to: Create a DataSet and Add a DataTable

 Creating a

DataSet

: – We can add a

DataSet

wizard.

to an application using the

Data Source Configuration

 Adding a

DataTable:

– We can add a

DataTable

wizard.

to a

DataSet

using the

Data Sources Configuration

How-to: Add a DataRow to a DataTable

 In order to add a new record into a

DataTable:

– First create a new

DataRow

(lines 6-8) – Assign values to the

DataColumns

(lines 11-13) – Add a new row to the

Rows

collection of a

DataTable

(line 16) Adding a

DataRow

to a

DataTable

How-to: Edit a DataRow in a DataTable

 In order to edit an existing row in a

DataTable

, we should first locate the

DataRow

, and then update its one or more columns. – Locate the

DataRow

using the

DataTable’s FindBy

by utilizing the row index. method or Editing a

DataRow

in a

DataTable

Editing a

DataRow

in a

DataTable

Using a Row Index 54

How-to: Delete a DataRow in a DataTable

 We can make use of the

Delete

method of a

DataRow

to delete a row – Again, we must find the row before we can delete it. Deleting a

DataRow

in a

DataTable

Deleting a

DataRow

from a

DataTable

Using a Row Index 55

How-to: Commit Changes in a DataSet

 The changes to

DataSet

are like changes in a Word document. – We must save the changes to update the

Dataset

– Initially, we check if the

DataSet

has been changed (line 55) – Then use its

AcceptChanges

method to commit insertions, edits, and deletions (line 57) Committing the Changes in a

DataSet

How-to: Filter and Sort Data

 We can filter data by using the

Filter

property of a

BindingSource

 We can sort data using the

Sort

property of the column name which we want to sort

BindingSource

on the –

Sort

property supports

DESC

and

ASC

sort ordering Filtering and Sorting Data Using the Properties of a

BindingSource

Object 57

Overview

            15.1 Introduction 15.2 ADO .NET Architecture 15.3 A Database Connection 15.4 Hands-On Tutorial: Displaying Data with Multiple Parameters 15.5 Hands-On Tutorial: Displaying Data from Join of Tables 15.6 Hands-On Tutorial: Displaying Data Using Access Query 15.7 Hands-On Tutorial: Passing Data between Forms 15.8 DataSets

15.9 Inserts, Updates, and Deletes in a Windows Application

15.10 Hands-On Tutorial: Updating Changes to Multiple Tables 15.11 In-Class Assignment 15.12 Summary 58

Data Flow from Windows Forms to a Database

 It is vital for an application to enable users to insert new data and edit, update, or delete existing data and then propagate those changes to the database – Two-stage propagating process:  Commit changes to

DataSet

 Commit changes to Database Two-Stage Propagating Process 59

Maintaining Information About Changes

 As a user makes changes in data-bind controls, the

DataSets

are automatically updated with the changes.

– The

DataRow

object keeps track of these changes and can be accessed using its properties. DataRow State Added Description The row that has been added to the

Rows

collection. Deleted Modified Unchanged The row that has been deleted. A column of the row that has been changed. Whether the row has been changed since the last call to

AcceptChanges

. 60

Retrieving Changed Rows

 It is also important that we are able to retrieve the changes made by a user. – Easily review the changes made by a user and possibly validate those changes before committing them to a database.

– Efficiently handle and work with only the changed portion of the

DataSet

rather than the entire

DataSet

. Usage Example

DataSet1

.GetChanges() Description Returns new

DataSet

with only changed records.

DataTable1

.GetChanges()

DataSet1

.GetChanges(DataRowState.Added) Returns new Returns new

DataTable DataSet

with only changed records. with only newly added records.

DataTable1

.GetChanges(DataRowState.Added) Returns new

DataTable

with only newly added records.

DataSet1

.GetChanges(DataRowState.Deleted) Returns new

DataSet

with only deleted records.

DataTable1

.GetChanges(DataRowState.Deleted) Returns new

DataTable

with only deleted records. 61

Committing Changes in the DataSet

 We can commit changes in the

DataSet

at: – The

DataRow

level – The

DataTable

level – The

DataSet

level Methods DataRow.AcceptChanges() DataTable.AcceptChanges() DataSet.AcceptChanges() Results Changes are committed only on the specific row Changes are committed on all rows in a specific table Changes are committed on all rows in all the tables of the DataSet 62

Build the Application

 How-to: Update (Save) Changes to the Database 1. Add a form (

Form6

) to the

AdvanceDBConnectivity

application.

2. Drag-and-drop the student

DataTable

on the form from the Data Sources Window. 3. Double-click the

Save

button on the

ToolStrip

to open the Code Window.

Build the Application and Test

4. Use the code below to complete the

TblStudentBindingNavigatorSaveItem_Click

event.

Saving Changes to the Database 5. Set

Form6

as the start-up object of the application. Press application. Test the application by changing values in the by saving the changes using the

ToolStrip’s Save

button.

Ctrl

to run the

DataGridView

and 64

Build the Application

 How-to: Insert and Delete Records in the Database 1. Add two command buttons named

cmdInsert

shown below. and

cmdDelete

Form6

, as

Form6

with Command Buttons to Insert and Delete Records 65

Build the Application

(cont.) 2. Replace the

Click

event code of the

cmdInsert

button with the code shown. 66

Build the Application

(cont.) – Replace the

Click

event code of the

cmdDelete

button with the code shown. 67

Test the Application

3. Ensure that

Form6

is set as the start-up form and press

Ctrl

to run the application. 4. Click the

Insert

button and insert the record [99999999, “James Adams”]. Adding a New Record to the Database 5. Now click the

Delete

button and delete the record inserted in previous step, by giving the

StudentID =

99999999 as input. MessageBox Showing the Record Deleted from the Database 68

Overview

15.10 Hands-On Tutorial: Updating Changes to Multiple Tables

15.11 In-Class Assignment 15.12 Summary 69

Build the Application

 How-to: Update Changes to Multiple Tables in the Database 1. Drag the related transcript table (under the student node) from the Data Sources Window on

Form6

. 2. Add a command button named

cmdSave

to the form. 3. Replace the

Click

event of the

Save

button with code shown below.

Update Code:

Part 1

Build the Application

(cont.) 3. (cont.) Replace the

Click

event of the

Save

button with code shown below.

Update Code:

Part 2

Build the Application

(cont.) 3. (cont.) Replace the

Click

event of the

Save

button with code shown below.

Update Code:

Part 3

Test the Application

4. Press

Ctrl

to run the application. 5. Change values in both the data grids and click

Save

. Update the record with the

StudentID =

10100118 so that

DeptID

= “

CISE”

and

Grade

= 3.6.

Running Application: Updating Multiple Tables in the Database 73

Overview

15.11 In-Class Assignment

15.12 Summary 74

In-Class Assignment

 Build an application with two forms: – The first form should display the output of Query1: 

“

List all the courses from the University database, where the course belongs to

College name

and has name

LIKE Course name

.” – Show the Query 1 output on a

DataGridView

Form1

. – When a user double clicks any course entry in the

DataGridView

, we should open the second form which displays the output of the following query: 

“

List all the sections that belongs to the course selected on the first form and have capacity of at least 40 students.” 75

Overview

15.12 Summary

Summary

(cont.)  ADO .NET objects interact from database to Windows forms: 1. A

Connection

object opens a live connection to the database. 2. A

DataAdapter

object executes Select SQL queries against the database.

3. The

DataAdapter

object further

fills

DataSet

object with query results.  The

DataSet

stores the results in the main memory.

 ADO .NET objects interact from Windows forms to database: 1. If a user edits the data in Windows controls, the updates are propagated to the

DataSet

object.

2. The

DataAdapter

object then propagates the updates from the

DataSet

object to the connected database by executing Update SQL statements.

Summary

(cont.)  Creating a database connection is like opening a unique session with the database. – Once opened, we can access contents of the database using the

Connection

object.

 We considered some advanced topics in displaying data on Windows forms. – How to display data from a query with multiple parameters.

– How to display data from a join of two or more tables.

– How to make use of existing MS Access queries to display data on forms.

– How to pass data between two Windows forms.

Summary

(cont.)  A

DataSet

is essentially an in-memory relational database. – A DataSet may contain one or more

DataTables.

– Each

DataTable

can have multiple

DataRows

and

DataColumns.

–

DataSets

act as a cache for a Windows application.

 We considered topics like how to insert, update, and delete rows from the database with the two-stage updates strategy. – Finally, to conclude the chapter, we showed how to handle propagation of changes to the database for related or multiple tables.