The information in this article applies to:
- Microsoft Access version 2.0
SUMMARY
This article demonstrates how you can create a sample user-defined Access
Basic function that calls itself multiple times in order to loop through a
linked list of items. You can use this technique to display data in a tree
structure such as a directory of managers and employees.
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 about Access Basic, please
refer to the "Building Applications" manual.
MORE INFORMATION
To create a sample user-defined Access Basic function that calls itself
multiple times, follow these steps:
- Open the sample database NWIND.MDB.
- Make a copy of the Employees table and name it Employees2.
- Open the Employees2 table in Design view.
- Change the name of the Employee ID field to EmpID.
- Change the name of the Reports To field to MgrID and set the MgrID
field's Indexed property to Yes(Duplicates OK).
- Save and close the Employees2 table.
- Create a module and type the following line in the Declarations section:
Option Explicit
- Type the following two procedures:
Function Start_List (EmpID As Long)
Dim db As Database, rs As Recordset
Set db = CurrentDB()
Set rs = db.OpenRecordset("Employees2", DB_OPEN_TABLE)
rs.Index = "Primarykey"
rs.Seek "=", EmpID
If rs.NoMatch Then Exit Function
Debug.Print EmpID & " " & rs![first name] & " "; rs![last name]
rs.Index = "MgrID"
List_Employees rs, EmpID, 1
rs.Close
db.Close
End Function
NOTE: In the following sample code, an underscore (_) at the end of a
line is used as a line-continuation character. Remove the underscore
from the end of the line when re-creating this code.
Sub List_Employees (rs As Recordset, ByVal MgrID As Long, ByVal _
level As Integer)
Dim bm As String
rs.Seek "=", MgrID
If rs.NoMatch Then Exit Sub
Do While Not rs.EOF
If rs!MgrID <> MgrID Then Exit Sub
Debug.Print String$(level,9) & rs!EmpID & " " & rs! _
[first name]& " "; rs![last name]
bm = rs.BookMark ' Save place in the recordset.
List_Employees rs, rs!EmpID, level + 1
rs.BookMark = bm ' Return to proper place for this level.
rs.MoveNext
Loop
End Sub
- To test this function, type the following line in the Immediate window,
and then press ENTER:
? Start_List(2)
Note that the records from the Employees2 table are displayed in a tree
format of managers and employees as follows:
2 Andrew Fuller
1 Nancy Davolio
3 Janet Leverling
11 Tim Smith
12 Caroline Patterson
4 Margaret Peacock
5 Steven Buchanan
6 Michael Suyama
7 Robert King
9 Anne Dodsworth
8 Laura Callahan
10 Albert Hellstern
13 Justin Brid
14 Xavier Martin
REFERENCES
Microsoft Access "Building Applications," version 2.0, Chapter 11, "Working
With Sets of Records," pages 242-267
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