Reports can be made quickly and easy for use with VB with Crystal Reports. But there are some problems you can encounter. For example if you use ODBC the name of the used DSN connection is saved within the report. Also when your users want to change the layout of the report they need a direct connection to the database. You can use views or a special user account to protect the structure of your database.
An other way is to make use of Data Definition files. They are just ASCII files which contains the fields and their properties that are to be used in the report. Using such a file means that there is no direct connection with the database. In Visual Basic the query is executed and the result – together with the Data Definition file – will produce the report.
To make it work you have to take three steps:
- making the Data Definition file
- making the report
- merge them in VB and show the result
The Biblio.mdb will be used in this example.
Step 1: making the Data Definition file
The report needs to be a view to be of all present authors with their titles and year of publication. The fields Author.Author, Titles.Tiltle and Titles.Year Published must be shown on the report. Due the keys the table Title Authors is used. The SQL to get the result is:
SELECT Authors.Author, Titles.Title, Titles.[Year Published]
FROM Titles INNER JOIN (Authors INNER JOIN [Title Author] ON Authors.Au_ID = [Title Author].Au_ID) ON Titles.ISBN = [Title Author].ISBN;
Making the Data Definition file can be done in Crystal Reports but also in any ordinary editor like notepad. The format is fixed:
All on one line separated by a TAB.
Author String 255 name
Title String 255 Title
YearPublished String 4 year
Don’t forget to save the file with the name: AuthorTitles.ttx Crystal Reports needs that to be able to define a report on this file.
Step 2: making the report
Start Crystal Report; choose for New, Standard report. On the tab Data select Active Data. On the next screen the choice is Data definition. Select with Browse the file you have made in step 1. Click on Finish. On the tab Fields select Add all and then Preview Report.
The report will be shown. As values the given descriptions will be shown. With Design you can change what you want on the report. Just save the report (standard extension .rpt). For quick merging in VB use the same name for the report as for the Data Definition file: AuthorTitles.rpt
Step 3: merge them in VB and show the result
Open a new project in VB (name = prjDDCR). Place on the default form (name = frmDDCR) a commandbutton (name = cmdShowReport; caption = Show report). Don’t forget to add the reference for DAO (Microsoft DAO Object Library ) and for Crystal Reports (Crystal Reports Engine Object Library).
Add the next code to the general section of the form. (It’s just an example so all values are hard-coded.)
Private db As DAO.Database
Private CDOSet As Object
Private RepApp As Object
Private CrystRep As CRPEAuto.Report
Private RepDb As CRPEAuto.Database
Private RepTables As CRPEAuto.DatabaseTables
Private RepTable As CRPEAuto.DatabaseTable
Private LabelRows() As Variant
On the Form_Load event add the next code. Don’t forget the code in the Form_Unload event! Change the path to the right location of your local Biblio.mdb
Private Sub Form_Load()
Set db = OpenDatabase(App.Path & “\biblio.mdb”)
Private Sub Form_Unload(Cancel As Integer)
Under the cmdShowReport_Click event is the code which merge the result of the executed SQL with the Data Definition file and the actual report.
Private Sub cmdShowReport_Click()
Dim strSQL As String
Dim rs As DAO.Recordset
Dim intFN As Integer
Dim strFN As String
Dim strLine As String
Dim intX As Integer
Dim intC As Integer
Dim intLabelCount As Integer
Set RepApp = CreateObject(“Crystal.CRPE.Application”)
Set CrystRep = RepApp.OpenReport(App.Path & “\AuthorTitles.rpt”)
Set CDOSet = CreateObject(“CrystalDataObject.CrystalComObject”)
intLabelCount = 0
intFN = FreeFile
strFN = App.Path & “\AuthorTitles.ttx”
Open strFN For Input As intFN
Do While Not EOF(intFN)
Line Input #intFN, strLine
If Len(strLine) <> 0 And Right(strLine, 2) <> “%%” Then
CDOSet.AddField Split(strLine, vbTab)(0), vbString
intLabelCount = intLabelCount + 1
strSQL = “SELECT Authors.Author, Titles.Title, Titles.[Year Published]” + _
” FROM Titles INNER JOIN (Authors INNER JOIN [Title Author] ON ” + _
” Authors.Au_ID = [Title Author].Au_ID) ON Titles.ISBN = [Title Author].ISBN;”
Set rs = db.OpenRecordset(strSQL)
If Not (.EOF And .BOF) Then
ReDim LabelRows(.RecordCount – 1, intLabelCount – 1)
For intX = LBound(LabelRows) To UBound(LabelRows)
For intC = 0 To .Fields.Count – 1
LabelRows(intX, intC) = CStr(“” & .Fields(intC).Value)
Set RepDb = CrystRep.Database
Set RepTables = RepDb.Tables
Set RepTable = RepTables(1)
Call RepTable.SetPrivateData(3, CDOSet)
Set rs = Nothing
Set RepApp = Nothing
Set CrystRep = Nothing
Set CDOSet = Nothing
Compile the project. Just hit the command button. Crystal Reports will open a separate window to show the result of the executed query in the report. You can open as much reports as you wish.
The advantage of using a Data Definition file is that no difficult solutions has to be made on the database side. You don’t have to make views available to the users. You don’t have to make a special user with only access to those tables you want. Adding a new report does not mean to be forced to compile a new executable. If you save the SQL and the Data Definition files in the database you only have to update the relevant tables. You can save the reports also in the database but it’s better to have them located outside the database. Showing all available reports form a certain location is just easy to do. Merging the three files together is just a simple extension on the example project.