Count and insert unique values - Can this code be optimized?

Question

I needed to generate an output from my Access database that was unavailable using standard functions. I did extensive searching, but when I found example code - it ultimately f

Answer 1

You can do this with an SQL query and a dash of VBA.

Insert a VBA module into Access, with the following code:

'Module level variables; values will persist between function calls
Dim lastValue As String 
Dim currentIndex As Integer

Public Function GetIndex(Value) As Integer
    If Value <> lastValue Then currentIndex = currentIndex + 1
    GetIndex = currentIndex
End Function

Public Sub Reset()
    lastValue = ""
    currentIndex = 0
End Sub

Then you can use the function as in the following query:

SELECT Table1.Field1, GetIndex([Field1]) AS Expr1
FROM Table1;

Just make sure to call Reset each time before you want to run the query; otherwise the last value will still be preserved from the previous query run.

---

When values later repeat themselves (e.g. a,b,a), the previous code will treat them as a new value. If you want the same value to return the same index for the entire length of a query, you can use a Dictionary:

Dim dict As New Scripting.Dictionary

Public Function GetIndex(Value As String) As Integer
    If Not dict.Exists(Value) Then dict(Value) = UBound(dict.Keys) + 1 'starting from 1
    GetIndex = dict(Value)
End Function

Public Sub Reset()
    Set dict = New Scripting.Dictionary
End Sub