8 db access using ado&report

8/18/2019 8 DB Access Using ADO&Report

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Data Bound Controls

And

Data Report Designer

Vivek Gupta

IT & Systems Group

Indian Institute of Management

Lucknow

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Using DataList, DataCombo &

DataGrid Controls


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DataList Control

• Allows us to display multiple rows of data in the same control,giving us a 'pick list' of values.

– Automatically filled with a field from a specified datacontrol.

– Selections from the list box can then be used to updateanother field from the same data control or, optionally, usedto update a field from another data control.

– Is not the same as the standard list control, which is notdata bound.

– To load this control, select Components from the Projectsmenu, then select from the Components dialog box:

• DAO Version:

– Microsoft Data Bound List Controls

• ADO Version:

– Microsoft DataList Controls

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DataList Control

• Data Bound List Control Properties:– BoundColumn: Name of field in Recordset specified by RowSourceto be passed to DataField, once selection is made.

– BoundText: Text value of BoundColumn field. This is the valuepassed to DataField property.

– DataField: Name of field in table specified by DataSource (orDataMember) updated by selection.

– DataSource: Name of data control (DAO or ADO) or dataenvironment (ADO) that is updated by the selection.

– DataMember: Specifies the Command object establishing the tableupdated by the selection (ADO data environment only).

– ListField: Name of field in table specified by RowSource (orRowMember) used to fill list box.

– RowMember: Specifies the Command object establishing the tableused by ListField (ADO data environment only).

– RowSource: Name of data control (DAO or ADO) or dataenvironment (ADO) used as source of items in list box.

– Text: Text value of selected item in list• Data Bound List Control Event :

– Click: Invoked when item in list control is clicked


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DataList Control• One use for the data bound list control is to fill the list (ListField)

from the database (RowSource), then allow selections.– This allows us to list all values of a particular field in a database

recordset.– The selections can be used by any control on a form, whether it is

data bound or not.

• A powerful feature of the data bound list control is linking to (andupdating) other fields in a database.

– This involves setting three more properties (DataSource, DataField,and BoundColumn).» RowSource is set to the data control establishing the recordset

providing the information listed (ListField) in the list box.• This establishes the source table.

» BoundColumn is the field name from the source table record usedas a link.

» DataSource is the recordset linked by the BoundColumn (it can bethe same recordset as RowSource or another recordset).

» Then, DataField is the field in DataSource that is linked byBoundColumn.

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DataCombo

• Nearly identical to the data bound list box.• Primary difference between the two controls is the

way data is displayed:

– the combo control has a list box portion and a text boxportion that displays the selected item, and,

– with the combo control, the user is (optionally) giventhe opportunity to type in a choice not in the list box.

– to load this control, select Components from theProjects menu, then select from the Componentsdialog box:

• DAO Version: Microsoft Data Bound List Controls

• ADO Version: Microsoft DataList Controls


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DataCombo• Data display is different with the combo control.

– Display is established by the Style property:• Style Symbolic Constant Description

0 VbComboDropDown Drop-down list box, usercan change selection

1 VbComboSimple Displayed list box, user

can change selection2 VbComboDropDownList Drop-down list box, usercannot change selection

• When using Style = 1, make sure you sufficiently size the control (sothe list box portion appears) when it is placed on the form.

• When to use the combo control instead of the list box control?– an excellent data entry control.– advantage over list box:

» it provides experienced users the ability to type in values they knoware correct, speeding up the data entry process.

• The list box control does not allow any typing.– It is also a good control when you are short on form space.– Using Style = 2 replicates the functionality of the list box control

without needing space for the list box.

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DataGrid

• One of the most useful data bound controls.– It can display an entire database table,

referenced by a data control.

» The table can then be edited as desired.

– To load this control, select Componentsfrom the Projects menu, then select from the

Components dialog box:

• DAO Version: Microsoft Data Bound Grid Control

• ADO Version: Microsoft DataGrid Control 6.0


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DataBound FlexGrid Controls• The data bound grid control is an excellent tool for providing

full-editing features in a spreadsheet like fashion.

– However, it is memory intensive and not real fast.

• If we only need display capabilities (no editing), consider thedata bound flexgrid control.

– This control offers an amazing array of variations in howdata can be displayed.

– To load this control, select Components from the Projectsmenu, then select from the Components dialog

• DAO/ADO Version: Microsoft FlexGrid Control

• The flexgrid control offers a wide number of properties thatallows us to display the data in any format we desire.– We can change the color and style of nearly every piece of

information in the grid (gridlines, fonts, colors, selections, …).

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The Vendors and New Vendor forms

DataCombo

DataList

Multiline text-

box

DataGrid


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Application description

• The DataCombo control on the Vendors form lets the user choose the name of a vendor from a drop-down list.

• If the user clicks on the New button on the Vendors form,the New Vendor form is displayed so the user can enter anew vendor.

• If the user clicks on the Delete button on the Vendors form,the current record is deleted. However, this button is disabledif the vendor has any unpaid invoices.

• The DataList control on the Vendors form displays theinvoice numbers for all of the selected vendor’s unpaidinvoices.

• The DataGrid control on the Vendors form displays detailinformation for all of the selected vendor’s unpaid invoices.

• The multi-line text box is just a text box with its MultiLine property set to true. In this application, it is used to displaysome of the fields in the vendor record.

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DataList and DataCombo propertiesProperty Description

DataSource The name of the data source that the control is

bound to. This is usually a data control or a

DataEnvironment object

DataMember If you select a DataEnvironment object for the

DataSource property, use this property to

select the Command object that you want to

useDataField The name of the field that the control is

bound to.


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DataList and DataCombo properties (continued)

Property Description

RowSource The name of the data source that provides the

data to be displayed. This is usually a data

control or a DataEnvironment object.RowMember If you select a DataEnvironment object for the

RowSource property, use this property to

select the Command object that you want to

use.

ListField The name of the field in the data source that’s

displayed by the control.

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DataList and DataCombo properties (continued)

Pro pe rty De s c rip tio n

BoundColumn The field defined by the RowSource property

that is used to pass data to the field defined

by the DataSource and DataField properties.

BoundText This property returns or sets the value of the

current field specified by the BoundColumn

property

DataFormat Determines the format in which the bound

data is displayed.

MatchEntry Determines how the data in a control issearched as text is entered.

Style (DataCombo only) Determines whether the

list portion of a combo box drops down or is

fixed. It also determines whether text can be

entered into the text portion of the box.


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DataCombo and DataList notes

• When you use a DataCombo and DataList control, you can bind the

control to a field that’s defined by one data control but display data from

a field that’s defined by another data control.

• The field that’s specified in the BoundColumn property is the field

that’s common to both of the recordsets that are defined by the data

controls.

• To bind a DataList or DataCombo control to a field, use the DataSourceand DataField properties. To display data in a DataList or DataCombo

control, use the RowSource and ListField properties.

• If you create a DataEnvironment object, you can use it for a DataSourceor RowSource property. In that case, you use the DataMember or

RowMember property to specify the command that you want to use

within the DataEnvironment object.

• Is this confusing? That's one of the problems with the use of boundforms. And if the properties aren't set right, the application doesn't work

right.

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The shortcut menu for a DataGrid control


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DataGrid notes

• You use the DataSource property of the DataGridcontrol to establish its source of data. This

property provides the name of the ADO data

control that the grid is bound to.

• Once you bind a DataGrid control to an ADO

data control, you can use the Retrieve Fieldscommand in the DataGrid’s shortcut menu to add

fields to the grid with each field as one column in

the DataGrid.

• If you choose the Edit command from its shortcutmenu, the DataGrid enters into UI-active mode.

In this mode, you can use the commands in the

UI-active shortcut menu to change the layout of

the columns and rows in the DataGrid control.

• The Cut, Copy, Paste, Delete, Insert, and Appendcommands in the UI-active shortcut menu let you

manipulate the columns in a DataGrid control.

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The Property Pages for a DataGridcontrol


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Common DataGrid properties

Tab Property

General AllowAddNew

General AllowDelete

General AllowUpdateColumns Caption

Columns DataField

Layout Locked

Layout AllowSizing

Layout Alignment

Format FormatType

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Database Reports

• Users expect to have the ability to obtain printedcopies of information contained within a database.

– This information is in the form of database reports.

– Generating reports is a straightforward task.

» We just need to determine what information we want inthe report and how we want it to be presented.

• Three approaches to developing database reports.

Each has its advantages and disadvantages.– The methods are:

» the Visual Basic Printer Object,

» the Crystal Reports report writer, and

» the ADO data environment Data Report capabilities


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ADO Data Environment Data Report• With VB6, Microsoft added a new way to produce database reports -

the Data Report.– This Data Report ability lets us build a report preview screen, with

print and export (even to the Internet) capabilities from an ADO dataenvironment (it will not work with the DAO or ADO data control).

– All we need to do is provide the data and establish the layout.– With future releases of VB, the Data Report is sure to become the

accepted standard for database reports.

• Like a Form, the Data Report has its own set of properties andmethods that control its appearance and use.

• The steps involved in using Data Report:– Set up the ADO recordset to be used by the report.– Add a Data Report object to your Visual Basic project.– Design the report by placing fields and other information on the Data

Report designer form.– Write code to display the report in your program

• The ADO Data Report capabilities are vast and using them is adetailed process.

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Data Report Properties• The Data Report has a number of properties that governs appearance

of the resulting report and how the report is connected to the datasource. Some important properties are:

– BorderStyle: Determines whether the displayed report window can beresized.

– Caption: Title information at top of data report window.– DataMember: Specifies the Command object establishing the database

report table.– DataSource: Name of data environment report is bound to.– BottomMargin: Bottom margin of printed report in twips.– TopMargin: Top margin of printed report in twips.– LeftMargin: Left margin of printed report in twips.– RightMargin: Right margin of printed report in twips.– ReportWidth: Width of database report in twips.– Title: Listed title for database report

• The three methods that control the database report:– ExportReport: Exports the report to a specified file (graphics cannot be

exported).– PrintReport: Sends the report to a printer.– Show: Displays the report in its own window.


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Data Report Designer

• To add a Data Report object to our VBapplication, click the Project menu item andselect Add Data Report. The Data Report

Designer appears.

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Data Report Designer• The Data Report is made up of five bands:

– Report Header: Information placed at the top of thedatabase report. Usually contains titling and dates.

– Page Header: Information placed at the top of each page inthe database report.

– Detail: Most critical section of report. Displays theinformation from the recordsets.

– Page Footer: Information placed at the bottom of each pagein the database report.

– Report Footer: Information placed at the end of the

database report.• Each band also has a Section Name.

– Each section has its own individual properties that can beaccessed at either design or run time.

– To display the properties for a particular section, click thesection's gray title bar.

– To display the properties for the Data Report object, clickthe square in the upper left corner of the designer.


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Data Report Designer• To build a database report, we place information on the

designer form.– This information is contained in a set of Data Report Tools.– When a data report is added to a VB project, a separate set

of tools is added to the toolbox.– To access these tools, click the Data Report button in the

toolbox (the usual tools are now accessed by clickingGeneral).

• The data report controls are:– rptLabel: Specifies a label used to display information that

is not data bound.– rptTextBox: Displays the contents of a database field.– rptImage : Contains a graphic image.– rptLine: Enables you to place lines on the report.

– rptShape: Enables you to place shapes on the report.– rptFunction: Allows you to place a field in the header or

footer with some computed summary information

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A new data report that’s based on aDataEnvironment object


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How to create a data report

• Before you create a data report, create aDataEnvironment object, a Connection object,

and a Command object that defines the data for

the report.

• Then, to create a data report, open the DataReport window.

• To associate the data report with the Commandobject you created, set the DataSource propertyof the report to the name of the DataEnvironment

object that contains the Command object, and set

the DataMember property to the name of the

Command object.

•

To format the sections of the report based on thestructure of the Command object, select theRetrieve Structure command from the shortcut

menu of the Data Report window.

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The design of a report


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How to work in the Data Report window

• To add a field to a report, drag it from the list of fieldsfor the Command object in the Data Environment

Designer window to the appropriate section of the report.

• When you add a field to a report, the DataMember andDataField properties of the text box that’s created are set

automatically so they refer to the appropriate field.

• You can also create a control that displays a field byadding a text box to the report and then setting its

DataMember and DataField properties manually.

• To add other controls to a report, select the control fromthe DataReport section of the Toolbox and then drag in

the report to place and size the control.

• To change the height of a section, drag the bottom border of the section. To change the width of all the sections inthe report, drag the right border of the report.

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The shortcut menu for inserting a predefined field


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Codes for predefined fields

Code Des cription

%p The current page number

%P The total number of pages

%d The current date (short format)

%D The current date (long format)

%t The current time (short format)

%T The current time (long format)

%i The report title (from the Title property of

the DataReport object)

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How to add a predefined field to a report

• Display the shortcut menu for the section where youwant to add the field and then select the field you want

to add from the Insert Control submenu.

• You can also include a predefined field by adding a labelcontrol and then including the code for the field in the

control’s Caption property.


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The vendor phone list report in print preview

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How to format, preview, and print a report

• To preview a report, set the Startup Object property of the project to the name of the data report. Then, run the

project.

• You can use the controls in the Print Preview window tozoom in and out of the report and to scroll through the

pages of the report. To print the report, click on the Print

toolbar button.

• To change the margins of a report or to control where page breaks occur, use the Report and Section properties.


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The properties for formatting a report for printing

Ob je c t Pro pe rty De s c riptio n

Report TopMargin

BottomMargin

LeftMargin

RightMargin

The margins of the report in

twips. By default, the margins

are set to 1440 (about one inch).

Section ForcePageBreak Forces a page break before or

after the section. The available

settings are rptPageBreakNone,

rptPageBreakBefore,

rptPageBreakAfter, and

rptPageBreakBeforeAndAfter.

KeepTogether Causes the section to begin

printing on the following page if the whole section won’t fit on

the current page.

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A report that groups invoices by vendor


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How to create groups based on fields

• You can use the Grouping tab in the Properties dialog box for a Command object to group the records retrieved

by the command.

• To create a group, check the Group Command Object

box, enter the name you want to use for the group, andselect the fields you want to include in the group.

• After you create a group, it will appear in the DataEnvironment Designer window with two subordinate

folders. The first folder contains the summary fields for

the group, and the second folder contains the detail

fields.

• If you base a report on a Command object that includesgrouping, the appropriate Group Header and Group

Footer sections are added to the report when you retrieve

the structure of the Command object.

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A report based on a command hierarchy


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How to create groups based onhierarchical relationships

• You can use the Data Environment Designer to

create a command hierarchy that consists of twoor more levels of parent-child relationships.

• When you retrieve the structure of a commandhierarchy into a data report, Group Header and

Group Footer sections are added to the report for

each parent command in the hierarchy.

• Then, you can add the fields in the parentcommands to the appropriate group sections, and

you can add the fields in the child command to

the Detail section.

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The syntax of the Show methodDatareport.Show

The syntax of the PrintReport methodDatareport.PrintReport [ShowDialog][,Range]

[,PageFrom][,PageTo]

Arg u me n t De s c rip tio n

ShowDialog Determines if the Print dialog box is displayed

before the report is printed.

Range Determines what pages of the report are printed.The available settings are rptRangeAllPages

(the default) and rptRangeFromTo.

PageFrom

PageTo

The numbers of the first and last pages to be

printed. If you omit PageFrom, the report is

printed from page 1. If you omit PageTo, the

report is printed through the last page.


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A statement that displays a report in Print PreviewdrVendorPhoneList.Show

A statement that displays the Print dialog box for areport

drYTDPurchases.PrintReport True

A statement that prints the first five pages of areportdrInvoicesByVendorDetail.PrintReport , rptRangeFromTo, , 5

Notes

• You can issue the Show or PrintReport method from a form or standard module.

• You can also export the text in a report to a file using theExportReport method.

How to create a data report without aDataEnvironment object

• Open a Connection object and create a Recordset object onthat connection using the Execute method. Then, set the

DataSource property of the data report to the Recordset

object.

• Because the DataReport object doesn’t have a Load event,you have to set its data source from a form or standard

module.

• When you design a data report that’s not associated with aDataEnviroment object, you include a field from the data

source by adding a text box to the report and then setting

its DataField property to the name of the field.

8 db access using ado&report

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