Violation of primary key issue

[firoz.raj]

Can anyone tell me ???.why i am getting the following issue ???.
Violation of PRIMARY KEY constraint 'PK_CNK_dailysales'. Cannot insert duplicate key in object 'CNK_dailysales'.
here is the following code what i have written

Public Sub InsertDailySales(rs As ADODB.Recordset)
Dim con As ADODB.Connection
Dim tempdate As Date
Dim strMsg$, StrMsgSales$
Dim TotalValue#
Dim totalQty%
If Not OpenConnection(con) Then
   MsgBox ("Connection is not open ")
   Set con = Nothing
   Exit Sub
End If
On Error GoTo errhnd
Dim TempSerial As String
TempSerial = ""
 rs.MoveFirst
 Do While Not rs.EOF
  If TempSerial <> rs!saleserial Then
     TempSerial = rs!saleserial
    If TempSerial <> "" Then
       con.Execute "Insert into interface.dbo.CNK_dailysales(Storeid,Saleserial,SaleInternalDate,dumpdate,nettotal) values('" & rs!StoreId & "','" & rs!saleserial & "','" & Format(rs!saleinternaldate, "YYYY-MM-DD") & "','" & Format(Now(), "YYYY-MM-DD HH:MM:SS") & "','" & "0" & "')"
    End If
End If
rs.MoveNext
Loop
strMsg = strMsg & rs!StoreId & " Total Sales" & vbTab & CDbl(TotalValue) & vbTab & " Total Qty" & vbTab & CInt(totalQty) & vbNewLine
            StrMsgSales = StrMsgSales & rs!StoreId & " Total Sales" & vbTab & CDbl(TotalValue) & vbTab & " Total Qty" & vbTab & CInt(totalQty) & vbNewLine
            ' Updating the Generated Files Date time Informations
            con.Execute "Update CNK_Stores set LastSaleDate='" & Format(DateAdd("d", 1, tempdate), "YYYY-MM-DD") & "' where INF_CODE='" & rs!StoreId & "'"
errhnd:
  Debug.Print Err.Description
'  Err.Clear
'  On Error GoTo 0
    
    
End Sub