Performance Issues


Thanks to Lada Simicek for this (and many other) tips.

How much faster is the selection of data from Microsoft Access database using SQL statement than DAO common statements? 

Many programmers do not take advantage of using SQL statements when working with DAO databases. This is generally because of the work involved learning of SQL language, compared to using common DAO statements. On the other hand SQL is very much faster and more powerful then DAO statements.

This short example shows how much is SQL statement faster then DAO statement. This program will find each author's name from Biblio.mdb (you should find this file in VB directory) that begins on the letter "S" and whose year of born was after 1930. You can simply compare the speed using SQL statement or DAO statement.

Be sure that in your application directory is located the file Biblio.mdb or change the line:

Set dbData = dbWork.OpenDatabase (App.Path & "Biblio.mdb")

In Project|References select Microsoft DAO 3.51 Object Library or Microsoft DAO 2.51 Object Library.

Add two buttons to the form, and set their Caption properties to the following:

Command1 - DAO
Command2 - SQL

Then, copy this code:

Private dbWork As Workspace
Private dbData As Database
Private dbTabl As Recordset
Private dblTime As Double
Private dbTablSQL As Recordset

Private I as Long

Private Sub Command2_Click()
    Debug.Print "_____________________________________________"
    dblTime = Timer
    Set dbTablSQL = dbData.OpenRecordset("SELECT * FROM " _
    & " [Authors] WHERE [Author] Like 'S*' And [Year Born] > 1930 ")

    For I = 0 To dbTablSQL.RecordCount - 1
        Debug.Print " Au_ID: " & dbTablSQL.Fields("[Au_ID]") _
        & ",   Author's name: " & dbTablSQL.Fields("[Author]") _
        & ",   Born: " & dbTablSQL.Fields _
        ("[Year Born]")
    Next I
    dblTime = (Timer - dblTime)
    Debug.Print "SQL time: " & dblTime

End Sub

Private Sub Command1_Click()

    Debug.Print "_____________________________________________"
    dblTime = Timer

    For I = 0 To dbTabl.RecordCount - 1
        If Left$(dbTabl.Fields("[Author]"), 1) = "S" And _
        dbTabl.Fields("[Year Born]") > 1930 Then
            Debug.Print " Au_ID: " & dbTabl.Fields("[Au_ID]") _
            & ",   Author's name: " & dbTabl.Fields("[Author]") _
            & ",   Born: " & dbTabl.Fields("[Year Born]")
        End If
    Next I
    dblTime = (Timer - dblTime)
    Debug.Print "DAO time: " & dblTime

End Sub

Private Sub Form_Load()
      Set dbWork = DBEngine.Workspaces(0)
      Set dbData = dbWork.OpenDatabase _
      (App.Path & "\Biblio.mdb") '//Set the path where _
      the file Biblio.mdb is located
      Set dbTabl = dbData.OpenRecordset("Authors", _
End Sub

Now, try it several times and compare the results.

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James Crowley

James Crowley United Kingdom

James first started this website when learning Visual Basic back in 1999 whilst studying his GCSEs. The site grew steadily over the years while being run as a hobby - to a regular monthly audien...

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