Generate random string in text field

Question

We have that old software (made by one of the first employees many years ago) in company that uses Microsoft Access to run. Boss asked me to add a random string generation i

Answer 1

Workin on @Bathsheba code, I did this. It will generate a random string with the number of characters you'd like.

Code :

Public Function GenerateUniqueSequence(numberOfCharacters As Integer) As String

    Dim random As String  ' * 8 'fixed length string with 8 characters
    Dim j As Integer
    Dim ch As Integer   ' each character

    random = ""

    For j = 1 To numberOfCharacters
        random = random & GenerateRandomAlphaNumericCharacter
    Next

    GenerateUniqueSequence = random

End Function

Public Function GenerateRandomAlphaNumericCharacter() As String

    'Numbers : 48 is '0', 57  is '9'
    'LETTERS : 65 is 'A', 90  is 'Z'
    'letters : 97 is 'a', 122 is 'z'

    GenerateRandomAlphaNumericCharacter = ""

    Dim i As Integer

    Randomize
    i = (Rnd() * 2) + 1 'One chance out of 3 to choose one of 3 catégories

    Randomize
    Select Case i
        Case 1 'Numbers
            GenerateRandomAlphaNumericCharacter = Chr(Rnd() * 9 + 48)
        Case 2 'LETTERS
            GenerateRandomAlphaNumericCharacter = Chr(Rnd() * 25 + 65)
        Case 3 'letters
            GenerateRandomAlphaNumericCharacter = Chr(Rnd() * 25 + 97)
    End Select

End Function

I use it with random number of characters, like this :

'Generates random Session ID between 15 and 30 alphanumeric characters
SessionID = GenerateUniqueSequence(Rnd * 15 + 15)

Result :

s8a8qWOmoDvC4jKRjPr5hOY12u 26
TB24qZ4cNfr6EdyY0J 18
6LZRQ9P5WHLNd71LIdqJ 20
KPN0RmlhhJKnVzPTkW 18
R2pNOKWJMKl9KpSoIV2egUNTEb1QC2 30
X8jHuupP6SvEI8Dt2wJi 20

NOTE: This is still not completely random. It will give a higher count of numbers than normal as approx 1/3 of all chars generated will be numbers.

Normally distribution will look like: 10 numbers plus 26 lowercase plus 26 uppercase = 62 possible chars. Numbers will normally be 10/62 parts of the string or 1/6.2
With the code i = (Rnd() * 2) + 1 'One chance out of 3 to choose one of 3 catégories the count of numbers is pushed up to 1/3 (on average)

Probably not too much of a worry - unless you are trying to beat the NSA and then you have decreased your range significantly.