VB3 How to Use TOP N Query from Microsoft Access 2.0 in VB

- Microsoft Visual Basic programming system for Windows, version 3.0

SUMMARY

One of the new types of queries added to Microsoft Access version 2.0 is called a TOP N query. If you have the Microsoft Jet 2.0/Visual Basic 3.0 Compatibility Layer, Microsoft Access version 2.0, and Visual Basic version 3.0, you can use this type of query from Visual Basic version 3.0 programs. This article gives a brief example that uses both the Microsoft 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:

      Sub Command1_Click ()
         Dim ds As Dynaset
         Dim db As database
   
         Set db = OpenDatabase("BIBLIO.MDB")
         ' Enter the following two lines as one, single line:
         Set ds =
            db.CreateDynaset("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:

      Sub Command2_Click ()
         Dim ds As Dynaset
         Dim db As database
   
         Set db = OpenDatabase("BIBLIO.MDB")
         ' Enter the following two lines as one, single line:
         Set ds = db.CreateDynaset("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:

      Sub Command3_Click ()
         Dim ds As Dynaset
         Dim db As database
   
         Set db = OpenDatabase("BIBLIO.MDB")
         ' Enter the following two lines as one, single line:
         Set ds = db.CreateDynaset("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. From the Run menu, choose Start (ALT, R, S), or press the F5 key to run the program. Click each of the buttons (Command1, Command2, and Command3) in succession.