How random are randomly generated numbers ?

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Hi there. Going straight to the problem. (Access 2000, Jet SP8, WinXP)

I have a table that has a string primary key, consisting of 25 numbers,
which are generated randomly using the following function:


Public Function NUMRandom(lowerbound As Long, upperbound As Long) As Long
NUMRandom = Int((upperbound - lowerbound + 1) * Rnd + lowerbound)
End Function

The function above is called from the following function:


Public Function APPCreateCode() As String
Dim s As String
Dim i As Integer

s = ""

For i = 1 To 25
Randomize
s = s & CStr(NUMRandom(0, 9))
Next

APPCreateCode= s
End Function

After a couple of weeks, this code started producing duplicate key values (I
don't know why, but I got an Access message when trying to insert.) After
this point, whenever the user pressed a button to insert a record, he always
got the duplicate key message. He had to click over twenty times, to get the
record inserted with a random primary key (and sometimes he' d give up
trying). So I changed the code a little as follows:


Public Function APPCreateCode() As String
Dim s As String
Dim i As Integer, j As Integer, li_rnd As Integer
Dim ls_temp As String

s = ""

Randomize
li_rnd = NUMRandom(1, 30)

For i = 1 To 25
For j = 1 To li_rnd
Randomize
ls_temp = CStr(NUMRandom(0, 9))
Next

s = s & ls_temp
Next

APPCreateCode= s
End Function
--------------
What I did, was to execute the randomize function a few more times (and also
for a random number of times in the inside loop. Then I gave the application
back to the client, and everything went well, but only for a couple of
weeks. Then the same problem occured again. Still the user got the duplicate
key message. This is an unexpected access behavior to me and I don't know
what I do wrong.


QUESTIONS:

1) How many characters are compared in the primary by Access, before
displaying the duplicate key message? (a) All of them in the key, or (b)
only a few?

2) If (a), then is there any better way of producing this primary key?

3) Is something wrong with the randomize and rnd functions?

TIA
Savvoulidis Iordanis
Greece



.

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