How to implement Query by Form (QBF) in an Access project (286828)

MORE INFORMATION

In an Access database (.mdb), you can use the query by form (QBF) technique to create a "query form" in which you enter criteria. The query form contains blank text boxes or combo boxes, each representing a field in your Access table that you want to query. You make entries only in the boxes for which you want to specify search criteria.

You can also implement the QBF technique in an Access project. In an Access project, you would use a stored procedure to find the records that you want to view, and then create an additional form to display the output of the stored procedure, as follows.

Creating a Stored Procedure

Follow these steps to create a stored procedure that you will use to return data to a form:

1. Open the sample Access project NorthwindCS.adp. By default, this file is installed in the <Drive>:\<Microsoft Access samples folder>.
2. On the Insert menu, and click Query.
3. In the New Query dialog box, click Create Text Stored Procedure, and then click OK.
4. Type the following Transact-SQL statements in the Stored Procedure window:

   Create Procedure "QBFProc"
       @CustomerID varchar(10), @EmployeeID int, @OrderDate datetime
       As
       Declare @SQLSTRING  varchar(1000)
       Declare @SelectList varchar(1000)
   
       SET NOCOUNT ON
   
       SELECT @SelectList = 'SELECT * FROM Orders'
   
       --Check to see if CustomerID search criteria is NULL.
       --If it contains a value, Begin to construct a WHERE clause.
       IF @CustomerID Is NOT NULL  
           BEGIN
               SELECT @SQLString = 'WHERE CustomerID = ''' + @CustomerID + ''''
           END
   
       --Check to see if EmployeeID search criteria is NULL. 
       --If it contains a value, add additional information to the WHERE clause.  
       IF @EmployeeID Is NOT NULL
           BEGIN
               IF @SQLSTRING Is NOT NULL 
                   BEGIN
                       SELECT @SQLSTRING = @SQLSTRING + ' AND EmployeeID = ' + Convert(varchar(100), @EmployeeID)
                   END
               ELSE 
                   BEGIN
                       SELECT @SQLSTRING = 'WHERE EmployeeID = ' + Convert(varchar(100), @EmployeeID)
                   END
           END
   
       --Check to see if OrderDate search criteria is NULL. 
       --If it contains a value, add additional information to the WHERE clause.  
       IF @OrderDate Is NOT NULL
           BEGIN
               IF @SQLSTRING Is NOT NULL 
                   BEGIN
                       SELECT @SQLSTRING = @SQLSTRING + ' AND OrderDate = ''' + Convert(varchar(20), @OrderDate) + ''''
                   END
               ELSE
                   BEGIN
                       SELECT @SQLSTRING = 'WHERE OrderDate = ''' + Convert(varchar(20), @OrderDate) + ''''
                   END
           END
   
       --Concatenate the SELECT and the WHERE clause together
       --unless all three parameters are null in which case return
       --@SelectList by itself without criteria.
       IF @CustomerID IS NULL AND @EmployeeID IS NULL AND @OrderDate IS NULL
   	BEGIN
   	    SELECT @SelectList = @SelectList
   	END
       ELSE
   	BEGIN
   	    SELECT @SelectList = @SelectList + ' ' +  @SQLSTRING
   	END
   
       --Execute the SQL statement.
       EXECUTE(@SELECTLIST)
   					

5. Save the stored procedure with the default name of QBFProc, and then close the procedure.

Creating the Query By Form

Follow these steps to create the QBF_Form form, which you will use to choose search criteria used by the stored procedure.

1. Create a new form that is not based on any table or query, and name it QBF_Form.
2. Make sure that the Control Wizards button is not pressed in in the toolbox, and then add three combo boxes to the form with the following property assignments:

      Combo Box:
      Name: cboCusID
      Row Source Type: Table/View/StoredProc
      Row Source: SELECT CustomerID FROM Customers
   
      Combo Box:
      Name: cboEmpID
      Row Source Type: Table/View/StoredProc
      Row Source: SELECT EmployeeID, LastName FROM Employees
      Column Count: 2
      Column Widths: 0;1
      Bound Column: 1
   
      Combo Box:
      Name: cboOrder
      Row Source Type: Table/View/StoredProc
      Row Source: SELECT OrderDate FROM Orders
   					

3. Add a command button to the form with the following property assignments:

      Name: cmdOpenFinal
      Caption: Open Form
      On Click: [Event Procedure]
   					

4. Click the Build (...) button to the right of [Event Procedure], and then set up the procedure as follows:

   Private Sub cmdOpenFinal_Click()
       DoCmd.OpenForm "frmFinal", acFormDS
   End Sub
   					

5. Save and then close the form, making sure to save the form as QBF_Form.

Creating the Form to Display the Results

Follow these steps to create the frmFinal form, which will display the results of the stored procedure based on the criteria that you enter in QBF_Form.

1. In the Database window, click Queries under Objects, and then click the QBFProc stored procedure so that it has the focus.
2. On the Insert menu, click AutoForm.
3. When you are prompted to enter a parameter, click Cancel.
4. Save the form that you just created as frmFinal.
5. Set the InputParameters property of this form to:

   @CustomerID varchar(10) = Forms!QBF_Form!cboCusID, @EmployeeID int = 
   Forms!QBF_Form!cboEmpID, @OrderDate datetime = Forms!QBF_Form!cboOrder
   					

6. Save and then close the frmFinal form.

To use the sample that you just created, open the QBF_Form form, and select values in any or all of the combo boxes. Click the command button to open the frmFinal form, which will display any matching records that meet the criteria that you selected in the QBF_Form form.