AutoNumber Regeneration

[jimfortune]

Sometimes I use Autonumber fields for ID fields. Furthermore,
sometimes I use those same fields in orderdetail type tables. So it's
important in that case that once an autonumber key value is assigned to
a record that it doesn't change. Occasionally I find that due to
corruption or an accidental deletion and restore of a record from a
backup the autonumber field needs to be tidied up. So when I create
(through AddNew) the autonumber key to be used for joins, I also save a
copy in a backup ID field (Long). I could get by with always using the
backup ID for the join but I don't like having backup ID's that are
different from the autonumber value. I decided that I really wanted to
regenerate the autonumber field to match the Backup ID values. I
couldn't get the 'force update on autonumber field to previously
deleted values' idea from a recent post to work so I created some code
to do it. It's still a little rough but might suffice to get someone
to point out an easier way. The code is in A97. I didn't have any RI
to deal with. The form shows the tables in the database and once the
table is selected, the fields populate two comboboxes for choosing the
primary key field and the backup ID field. txtNewTableName is for the
name of the new table with the repaired autonumber values. The main
idea is to use AddNew without an Update until the next backup ID is
reached.

'-------Form Code
Option Compare Database
Option Explicit

Private Sub cbxDatabaseTabl e_AfterUpdate()
Dim MyDB As Database
Dim tdf As TableDef
Dim fld As Field

If IsNull(cbxDatab aseTable.Value) Then
cbxIDFieldName. RowSource = ""
cbxBackupIDFiel dName.RowSource = ""
cbxIDFieldName. Value = Null
cbxBackupIDFiel dName.Value = Null
Exit Sub
End If
'Put the field names in cbxIDFieldName and cbxBackupIDFiel dName
Set MyDB = CurrentDb
cbxIDFieldName. RowSourceType = "Value List"
cbxBackupIDFiel dName.RowSource Type = "Value List"
For Each fld In MyDB.TableDefs( cbxDatabaseTabl e.Value).Fields
If Nz(cbxIDFieldNa me.RowSource, "") = "" Then
cbxIDFieldName. RowSource = fld.Name
Else
cbxIDFieldName. RowSource = cbxIDFieldName. RowSource _
& ";" & fld.Name
End If
If Nz(cbxBackupIDF ieldName.RowSou rce, "") = "" Then
cbxBackupIDFiel dName.RowSource = fld.Name
Else
cbxBackupIDFiel dName.RowSource = cbxBackupIDFiel dName.RowSource _
& ";" & fld.Name
End If
Next fld
Set MyDB = Nothing
End Sub

Private Sub cmdFixAutonumbe r_Click()
If IsNull(cbxDatab aseTable.Value) Then
MsgBox ("No table was selected.")
Exit Sub
End If
If IsNull(txtNewTa bleName.Value) Then
MsgBox ("No new table name was selected.")
Exit Sub
End If
If IsNull(cbxIDFie ldName.Value) Then
MsgBox ("No ID Field was selected.")
Exit Sub
End If
If IsNull(cbxBacku pIDFieldName.Va lue) Then
MsgBox ("No Backup ID Field was selected.")
Exit Sub
End If
Call FixAutoNumber(c bxDatabaseTable .Value, txtNewTableName .Value, _
cbxIDFieldName. Value, cbxBackupIDFiel dName.Value)
MsgBox ("Done.")
End Sub

Private Sub Form_Load()
Dim MyDB As Database
Dim tdfLoop As TableDef

Set MyDB = CurrentDb
cbxDatabaseTabl e.RowSourceType = "Value List"
For Each tdfLoop In MyDB.TableDefs
If Left(tdfLoop.Na me, 4) <> "MSys" Then
If Nz(cbxDatabaseT able.RowSource, "") = "" Then
cbxDatabaseTabl e.RowSource = tdfLoop.Name
Else
cbxDatabaseTabl e.RowSource = cbxDatabaseTabl e.RowSource _
& ";" & tdfLoop.Name
End If
End If
Next
Set MyDB = Nothing
End Sub
'-------End Form Code

'-------Module Code
Option Compare Database
Option Explicit

Public Sub FixAutoNumber(s trOriginal As String, strNew As String, _
strIDFieldName As String, strBackupIDFiel dName As String)
Dim MyDB As Database
Dim AutoRS As Recordset
Dim NewRS As Recordset
Dim strSQL As String
Dim tdfAuto As TableDef
Dim fldAuto As Field
Dim lngCount As Long
Dim lngI As Long
Dim lngKey As Long
Dim tdf As TableDef
Dim fld As Field
Dim idxAuto As Index
Dim idx As Index
Dim boolFound As Boolean

'Place contents of table called strOriginal into table called
'strNew whenever the new autonumber matches BackupID
Set MyDB = CurrentDb
'Make sure index names and fields match
For Each idxAuto In MyDB.TableDefs( strOriginal).In dexes
If idxAuto.Name <> "PrimaryKey " Then
boolFound = False
For Each fld In idxAuto.Fields
If idxAuto.Name = fld.Name Then
boolFound = True
Exit For
End If
Next fld
If boolFound = False Then
MsgBox ("An index name doesn't match a field name.")
Set MyDB = Nothing
Exit Sub
End If
End If
Next idxAuto
'Delete the new table if it already exists
For Each tdf In MyDB.TableDefs
If tdf.Name = strNew Then
MyDB.Execute "DROP TABLE " & strNew & ";"
Exit For
End If
Next tdf
Set tdf = MyDB.CreateTabl eDef(strNew)
Set tdfAuto = MyDB.TableDefs( strOriginal)
For Each fldAuto In tdfAuto.Fields
If fldAuto.Type = dbText Then
Set fld = tdf.CreateField (fldAuto.Name, dbText, fldAuto.Size)
Else
Set fld = tdf.CreateField (fldAuto.Name, fldAuto.Type)
fld.Attributes = fldAuto.Attribu tes
End If
tdf.Fields.Appe nd fld
Next fldAuto
MyDB.TableDefs. Append tdf
tdf.Fields.Refr esh
For Each idxAuto In MyDB.TableDefs( strOriginal).In dexes
If idxAuto.Name <> "PrimaryKey " Then
Set idx = tdf.CreateIndex (idxAuto.Name)
If idxAuto.Name = strIDFieldName Then idx.Primary = True
If idxAuto.Require d Then idx.Required = True
idx.Fields.Appe nd idx.CreateField (idxAuto.Name)
tdf.Indexes.App end idx
End If
Next idxAuto
tdf.Indexes.Ref resh
DoEvents
strSQL = "SELECT * FROM " & strOriginal & " ORDER BY " _
& strBackupIDFiel dName & ";"
Set AutoRS = MyDB.OpenRecord set(strSQL, dbOpenSnapshot)
strSQL = "SELECT * FROM " & strNew & ";"
Set NewRS = MyDB.OpenRecord set(strSQL, dbOpenDynaset)
If AutoRS.RecordCo unt > 0 Then
AutoRS.MoveLast
lngCount = AutoRS.RecordCo unt
AutoRS.MoveFirs t
For lngI = 1 To lngCount
lngKey = 0
Do Until lngKey = AutoRS(strBacku pIDFieldName)
NewRS.AddNew
DoEvents
lngKey = NewRS(strIDFiel dName)
Loop
For Each fldAuto In tdfAuto.Fields
If fldAuto.Name <> strIDFieldName Then
NewRS(fldAuto.N ame) = AutoRS(fldAuto. Name)
End If
Next fldAuto
NewRS.Update
If lngI <> lngCount Then AutoRS.MoveNext
Next lngI
End If
AutoRS.Close
Set AutoRS = Nothing
NewRS.Close
Set NewRS = Nothing
Set MyDB = Nothing
End Sub
'-------End Module Code

James A. Fortune

[David W. Fenton]

Steve Jorgensen <no****@nospam. nospam> wrote in
news:n6******** *************** *********@4ax.c om:

On Wed, 15 Dec 2004 19:43:38 GMT, "David W. Fenton"
<dX********@bw ay.net.invalid> wrote:

Steve Jorgensen <no****@nospam. nospam> wrote in
news:t4****** *************** ***********@4ax .com:

On Wed, 15 Dec 2004 02:51:19 GMT, "David W. Fenton"
<dX********@ bway.net.invali d> wrote:

rkc <rk*@rochester. yabba.dabba.do. rr.bomb> wrote in
news:Ov**** *************** @twister.nyroc. rr.com:

> Tony Toews wrote:
>> "Tony D'Ambra" <td*****@swiftd sl.com.au> wrote:
>
>>>The negative side is that the
>>>applicat ion stands a much better chance of failing if the
>>>AutoNumb ered values become corrupt.
>>
>>
>> This was a problem in some versions of Jet 4.0 but SPs fixed
>> those. While I still mostly work in A97 I've never had a
>> problem with Autonumber values becoming corrupt.
>
> What are the symptoms of a corrupt autonumber field? Do the
> values already stored mysteriously change or are duplicates
> suddenly allowed in a primary key field?
>
> Or something else?

The most common is the "loss of seed value" error, where each
new record gets the same Autonumber, sometimes a previously-used
value, sometimes not.

This was a very common weakness in the first versions of Jet 4,
one that I'd never seen in any previous version of Jet. It was
fixed about SP4 or so, if I'm remembering correctly.

Of course, it wasn't until SP6 that Jet 4 was really stable.

Actually, the seed problem is much improved, but not fixed. In
a networked environment with a large number of simultaneous
users, it still happens fairly regularly in my experience.

I haven't seen it at any of my clients since SP4.

How many simultaneous users are you talking about?

Well, lots. The place I was working where it was happening
routinely had over 100 users hitting the same back-end.

Heavens! I've never had anything that large, and wouldn't be very
comfortable with it at all!

Well, that's good to know as another reason to try to convince
clients to move to a server back end when they get into the 50+
users territory.

--
David W. Fenton http://www.bway.net/~dfenton
dfenton at bway dot net http://www.bway.net/~dfassoc

[david epsom dot com dot au]

> They also get re-used when someone dies.

Not deliberately. The location of the SSN FAQ has changed:
it is now here:

http://archive.cpsr.org/cpsr/privacy/ssn/ssn.faq.html

Most of the links in that document are broken. The discussion
of problems with the use of SSN's as primary keys is here:

http://archive.cpsr.org/cpsr/privacy...-addendum.html

(david)

"Trevor Best" <no****@besty.o rg.uk> wrote in message
news:41******** **************@ news.zen.co.uk. ..

Rick Brandt wrote:

"Bas Cost Budde" <b.*********@he uvelqop.nl> wrote in message
news:cp******** **@news2.solcon .nl...

Tony Toews wrote:
how do you get a natural key for a person? SSN? No.

Hey! Why not? I am not familiar with SSN but there is a pendant
structure in Holland, the number should be unique. Is SSN not?

From what I hear "it's supposed to be" would be the answer to your
question. Fraud and screw-ups dictate otherwise.

They also get re-used when someone dies.

--
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[Larry Linson]

"Tony D'Ambra" wrote

Firstly, I find your use of "Eh?" offensive.
Your MVP status does not exempt
you from the rules of simple courtesy...

It's a Canadian speech habit thing that carries over into writing... not
intended to be offensive nor discourteous. Perhaps it has some different
meaning or usage in Oz?

[Larry Linson]

"Steve Jorgensen" wrote

Well, lots. The place I was working
where it was happening routinely had
over 100 users hitting the same
back-end.

Ah, that is near-record territory. Consider yourself added to the "people
whose observations we can trust" when we talk about the upper limits of
multiuser. Hey, it's good company, including michka, Stephen Forte, Drew
Wutka, and Mike Groh...

Like David, I don't have personal experience with that size user audience.
But that is quite a lot of users, and likely to stress a poor little
"desktop database" somewhat. But, as David also said, it'd be worth a check
that all users are up-to-date with SPs for Jet 4. Wouldn't it be nice if
that were a solvable problem, and you solved it for your client?

Larry Linson
Microsoft Access MVP

[rkc]

Larry Linson wrote:

"Tony D'Ambra" wrote

> Firstly, I find your use of "Eh?" offensive.
> Your MVP status does not exempt
> you from the rules of simple courtesy...

It's a Canadian speech habit thing that carries over into writing... not
intended to be offensive nor discourteous. Perhaps it has some different
meaning or usage in Oz?

Interesting spin. In my experience "Eh?" is usually tacked on to
the end of a sentence by afore referenced Canadians.

[Larry Linson]

"rkc" wrote

Interesting spin. In my experience "Eh?" is usually tacked on to
the end of a sentence by afore referenced Canadians.

That, too. I took Tony's use to be more-or-less equivalent to my saying
something like: "Interestin g. My own observation is...".

Larry Linson

[Trevor Best]

Larry Linson wrote:

"rkc" wrote

Interesting spin. In my experience "Eh?" is usually tacked on to
the end of a sentence by afore referenced Canadians.

That, too. I took Tony's use to be more-or-less equivalent to my saying
something like: "Interestin g. My own observation is...".

Bejeezus, that's what I thought :-)

--
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