ACC2: How to Find a Record Using a Bound Control

• Microsoft Access version 2.0

SUMMARY

Moderate: Requires basic macro, coding, and interoperability skills.

This article demonstrates how to use a single bound control both for finding records and entering data in a form.

You can use this technique to find whether the value entered in a field already exists in another record. If the value does exist in another record, the record containing that value will be displayed. If the value does not exist in another record, you can continue entering data for the current record.

This article assumes that you are familiar with Access Basic and with creating Microsoft Access applications using the programming tools provided with Microsoft Access. For more information on Access Basic, please refer to the "Building Applications" manual.

MORE INFORMATION

The Microsoft Access "User's Guide" demonstrates a method that you can use to find records in your database by selecting a key value from a list. (See "Finding a Record by Selecting a Value from a List.") This method is limited in that it requires two controls. One control is an unbound control that is used to select the value to look for, and the other control is a bound control in which data entry for that value occurs.

The following example demonstrates how to use a single, bound control to achieve the same functionality.

NOTE: The field to which the control is bound cannot be a required field and it cannot have a validation rule that allows null values. Make sure that the field's Required property is set to No and that its ValidationRule property does not allow null values.

1. Open the sample database NWIND.MDB. Create a new module with the following declarations and functions:

         ' *******************************************************
         ' DECLARATIONS SECTION
         ' *******************************************************
         Option Explicit
         Dim Found
   

         Function Find_BeforeUpdate (F As Form)
            Dim RS As Recordset, C As Control
            Set C = Screen.ActiveControl
            Set RS = F.RecordsetClone
   
            On Error Goto Err_Find_BeforeUpdate
   
            ' Try to find a record with a matching value.
            Select Case RS.Fields(C.ControlSource).Type
               ' Find using numeric data type key value?
               Case DB_INTEGER, DB_LONG, DB_CURRENCY, DB_SINGLE, _
               DB_DOUBLE, DB_BYTE
                  RS.FindFirst "[" & C.ControlSource & "]=" & C
               ' Find using date data type key value?
               Case DB_DATE
                  RS.FindFirst "[" & C.ControlSource & "]=#" & C & "#"
               ' Find using text data type key value?
               Case DB_TEXT
                  RS.FindFirst "[" & C.ControlSource & "] = """ & C & """"
               Case Else
                  MsgBox "ERROR: Invalid data type for '" & C.Name & "'!"
                  DoCmd CancelEvent
                  Exit Function
            End Select
   
            ' If a record was found, save the found record's bookmark.
            If RS.NoMatch Then
               Found = Null
            Else
               Found = RS.Bookmark
            End If
   
            ' If the record was found...
            ' ...cancel the BeforeUpdate event
            ' ...undo changes made to the current record
            ' ...and TAB to the next control to trigger the OnExit routine.
            If Not IsNull(Found) Then
               DoCmd CancelEvent
               SendKeys "{ESC 2}{TAB}", False
            End If
   
            Exit Function
   
         Err_Find_BeforeUpdate:
            MsgBox "ERROR: Err " & Err & ": " & Error$, 48
            DoCmd CancelEvent
            Exit Function
   
         End Function
   
         Function Find_OnExit ()
            ' If the record was found, cancel the OnExit routine to stay
            ' in the control and go find the record.
            If Not IsNull(Found) And Found <> "" Then
               DoCmd CancelEvent
   
               ' Synchronize the form record with the found record.
               Screen.ActiveForm.Bookmark = Found
   
               Found = Null
            End If
         End Function
   
   

2. Open the Customers form in Design view. Change the following properties for the Customer ID field:

         BeforeUpdate: =Find_BeforeUpdate(Form)
         OnExit: =Find_OnExit()
   

3. View the form in Form view. In the Customer ID field, type "AROUT" (without quotation marks) and then press ENTER. Microsoft Access will find and display the Around The Horn customer.

4. In the Customer ID field, type "POPSI" (without quotation marks) and then press ENTER. Since this key value does not exist, you can continue entering data for the record.

How the Sample Functions Work

The Find_BeforeUpdate() function uses the FindFirst method to search the dynaset the form is based on to see if the value entered in the control exists in the table.

If the value does not exist, the global variable Found is set to NULL and the function exits. If the value does exist, the global variable Found is set to the bookmark of the found record to be used by the Find_OnExit() function.

Before the found record can be presented, the BeforeUpdate event must be canceled, and a SendKeys action must send two ESC keys to undo changes to the current record.

Next, the SendKeys action sends a TAB key to exit the field. This event triggers the Find_OnExit() function, which checks to see if the find was successful. If it was, the CancelEvent action is run to prevent exiting the control, and then the form record is synchronized with the found record by setting its bookmark equal to the bookmark of the found record. Found is then reset back to NULL.

REFERENCES

Microsoft Access "User's Guide," version 2.0, Chapter 25, "Using Macros and Forms," pages 651-652