HOWTO: Use TOP N Query from Microsoft Access 2.0 in VB

• Microsoft Visual Basic for Windows Professional and Enterprise Editions, versions 5.0, 6.0
• Professional and Enterprise Editions of Microsoft Visual Basic, 16-bit only, for Windows, version 4.0
• Microsoft Access for Windows

SUMMARY

One of the new types of queries added to Microsoft Access version 2.0 for Windows is called a TOP N query. If you have Microsoft Access version 2.0 or higher, and Microsoft Visual Basic for Windows version 4.0 and higher, you can use this type of query from Visual Basic version 4.0 programs.

This article gives a brief example that uses both the Access TOP N and TOP N PERCENT queries from Visual Basic.

MORE INFORMATION

For more information on these particular queries, please review the Microsoft Access documentation.

Step-by-Step Example

1. Start a new project in Visual Basic. Form1 is created by default.



2. Add three Labels, three List Box controls, and three Command buttons to Form1.



3. Using the following table as a guide, set the properties of the controls you added in step 2:




   Control Name   Property       New Value
   --------------------------------------------------------------------

   Label1         Caption        Selecting the first 10 titles from the
                                 Titles table according to title field.
   Label2         Caption        Selecting the first 5 titles from the
                                 Titles table according to date published.
   Label3         Caption        Selecting the first 7 years of percent
                                 published from the Titles table according
                                 to the year published field.
   Command1       Caption        First 10 Title names.
   Command2       Caption        First 5 titles dates published.
   Command3       Caption        First 7 years percent published. 

4. Place the following code in the Command1 Click event procedure:




   Private Sub Command1_Click ()
      Dim ds As Recordset
      Dim db As database

      Set db = Workspaces(0).OpenDatabase("BIBLIO.MDB")
      Set ds = _
         db.OpenRecordset("select top 5 title from titles order by title")

      Do Until ds.EOF
         list1.AddItem "" & ds("title")
         ds.MoveNext
      Loop
      ds.Close
      db.Close
   End Sub 

5. Place the following code in the Command2 Click event procedure:




   Private Sub Command2_Click ()
      Dim ds As Recordset
      Dim db As database

      Set db = Workspaces(0).OpenDatabase("BIBLIO.MDB")
      Set ds = db.OpenRecordset("select top 5 [year published], _
         title from titles order by [year published]")

      Do Until ds.EOF
         list2.AddItem "" & ds("title")
         ds.MoveNext
      Loop
      ds.Close
      db.Close
   End Sub 

6. Place the following code in the Command3 Click event procedure:




   Private Sub Command3_Click ()
      Dim ds As Recordset
      Dim db As database

      Set db = Workspaces(0).OpenDatabase("BIBLIO.MDB")
      Set ds = db.OpenRecordset("select top 7 Percent [year published], _
         title from titles order by [year published]")

      Do Until ds.EOF
         list3.AddItem "" & ds("title")
         ds.MoveNext
      Loop
      ds.Close
      db.Close
   End Sub 

7. On the Run menu, click Start (ALT, R, S), or press the F5 key to run the program. Click each of the buttons (Command1, Command2, and Command3) in succession.

Additional query words: kbVBp400 kbVBp500 kbVBp600 kbdse kbDSupport kbVBp

Keywords : kbGrpVBDB
Version : WINDOWS:
Platform : WINDOWS
Issue type :