Re: Help with first VB application - Data Entry form

Every app is different and has different requirements, you know that.
Having said that, using a PK that is, in part (not completely), time based
is the best way to avoid concurrency issues. Just about every book and
enterprise application I've read and worked with follow this approach. Does
that make it "law", no. In development there are a number of different ways
to solve any problem. If you have one that works for you, great.

"jeff" <jhersey at allnorth dottt com> wrote in message
news:eZ05n9TvGHA.1808@xxxxxxxxxxxxxxxxxxxxxxx
Scottt...

I have done a small poll ... and people I have asked and responded, have
never used a timestamp / datetime field as part of their PK set ... and
the one fella that did (or at least was brought in to a project after
design), had to go back and re-write them, cause he was getting too many
transactions, and the app would flequently encounter collisions due to the
timestamp / composite key approach.

So, I will remain in the 'minority' (quite a large on from where I sit)
and keep 'not' using timestamps / datatime fields in my PK's ....
surrogate key approach works just fine for me.

Thanks.
Jeff.


"jeff" <jhersey at allnorth dottt com> wrote in message
news:eijOk4AvGHA.4752@xxxxxxxxxxxxxxxxxxxxxxx

Scott.

agree...I had assumed a winform application...since the OP stated using
Scanning hardware .... I assumed a desktop / winform client application
... and that is why I had given a SELECT script for obtaining a 'date
time' stamp from the database machine - control machine ... and for this
example, the database machine was the easiest ... unless there is an
easier way to obtain a date time value from another machine - that the
client machine 'knows' about ?

agree...if a webform / asp.net application ... script executes on server
... problem solved - web server is control system. would not want to
pull unnecessary data to the client ...

Jeff.

PS: I do not lilke using the time-stamp approach with PK's for the simple
reason that all database venders handle dates and times slightly
different - and when building a database independent UI / Client - Server
application, I find it much easier to code a framework without them ...
if this puts me in the minority, I will need to do a bit more research to
convince me otherwise.



"Scott M." <s-mar@xxxxxxxxxxxxx> wrote in message
news:%23b2S7hAvGHA.3428@xxxxxxxxxxxxxxxxxxxxxxx
I did just realize though, that you and I have been assuming 2 different
fundmental things...

I have been assuming this is an ASP.NET web application, hence my last
comment:

I did suggest this code, but this is server-side code (not client-side
JavaScript, for example) and thus, will get the time from the web
server, not the client. VB.NET code (or any .NET code for that matter)
does not function on the client.

I think you have been commenting from the point of a WinForms
application. If that is the case (the OP didn't specify), then you are
correct, the code would execute on the client.


"Scott M." <s-mar@xxxxxxxxxxxxx> wrote in message
news:ebiX1eAvGHA.724@xxxxxxxxxxxxxxxxxxxxxxx
PS... never mentioned time based PK for you to agree with ... I do not
like these and avoid them.

Well, you are in the minority on that one. Having a PK that is, in
part, time stamped is the best way to avoid data concurrency issues
when doing updates, inserts and deletes.

PPS. you suggested the client get the time stamp ... txtDate.Text =
Now.ToShortDateString

I did suggest this code, but this is server-side code (not client-side
JavaScript, for example) and thus, will get the time from the web
server, not the client. VB.NET code (or any .NET code for that matter)
does not function on the client.




"Scott M." <s-mar@xxxxxxxxxxxxx> wrote in message
news:%23fifBb$uGHA.1296@xxxxxxxxxxxxxxxxxxxxxxx
Yes, but again, I don't think anyone was suggesting the client in the
first place.

In my opinion, the database is not the place to put a time stamp of
this kind. While I agree that good primary keys are partially time
based, this is not what the OP has stated the time would be used for.
The time is going to become data that is used by the business layer
of the applicaiton. Databases should not be in charge of creating
business data in this manner.

"jeff" <jhersey at allnorth dottt com> wrote in message
news:OvnwS49uGHA.324@xxxxxxxxxxxxxxxxxxxxxxx

...exactly... my point.

what if you have multiple clients in different time zones ...
multiple web servers in different time zones ... and multiple
databases servers in different time zones... with a user from one
time zone, connecting to a web server in another and a database in a
third ... and the next time the user log-ins ... same CLIENT machine
... he hits a different web server and different database for his
next scan transaction ... you need some type of 'control' in the
date stamping ... and to me the logical one is the Database Server.

you need to set a base line for time stamping ... and to me, relying
on the CLIENT for this, is not good practice...as per you
suggestion...

Sub Button1_Click() Handles Button1.Click
txtDate.Text = Now.ToShortDateString
End Sub

I simply made a suggestion to use the database as the control date /
time 'stamper' (for lack of a better term). If you have different
databases in different time zones, when you synchronize your data
... if you are not identifying which server the record was initially
created on, you offset you timestamps accordingly during the sync
process ... or when you build a consolidated report to include data
from other database servers in different timezones, you offset your
timestamps based on the database server's 'timezone' ...

relying on the CLIENT is poor practice and has a hard time standing
up to an audit ... unless you have a mechanism / policy in place
that controls the time on a CLIENT machines.

Just my 2 cents ... just offering a suggestion thats all.

Jeff

"Scott M." <s-mar@xxxxxxxxxxxxx> wrote in message
news:eHymO18uGHA.1224@xxxxxxxxxxxxxxxxxxxxxxx
Hold on Jeff. What if the client, web server and database are in
diffeent time zones? I don't think anyone suggested using the
client for the date, but I think the server should generate that,
not the database.




"jeff" <jhersey at allnorth dottt com> wrote in message
news:ezBzQv6uGHA.4972@xxxxxxxxxxxxxxxxxxxxxxx

Comment...

Getting the Date / Time from the 'client' machine can lead to
'false' date / time stamping...ie the user has messed with the
system clock and so on ... If this time will be used for control /
report purposes, I would recommend either ...

a. Have the database fill the datetime stamp with a default
obtained from the server ...

b. Create a function to get the current date / time from the
server or a common source.

Question - What do you considered the 'Time Stamp' for the scan
... when item is scanned or when the record is saved ... if
scanned, you will need to get the date from a common source ... if
saved, set the default value in the data table to get the current
date time on the server and only issue an insert with the text
field... and let the server fill the date/time stamp.

Jeff.

PS:

b: - Get a data from a common place...

Assuming MSSQL Server Database...
SELECT GetDate();
using a ExecuteScaler on an OLEDBConnection ...

Using MSAccess...
SELECT Now();
using a ExecuteScaler on an OLEDBConnection.




<Timothy.Rybak@xxxxxxxxx> wrote in message
news:1155061620.089944.269190@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hello all,

This is my first attempt at an application, so kid gloves are
appreciated.

I need to make a very simple form that only has a few elements.
One is
TraceCode - a text field that is populated when a user scans a
label.
The other is ScanDate - a date/time field that should equal the
date/time of the scan (e.g. 7/31/2006 5:00:00 AM).

When a button is clicked, or Enter is pressed on the keyboard (or
as
the last character of the scan), the data should be transmitted
to a
SQL table, and the two text field should be cleared and ready for
the
next scan.

Currently, I have a simple form, but you have to manually type
the
ScanDate. Also, the fields don't clear after the update is
successful.

Ideally, there would only be one textbox available to the user,
and
when they scan the TraceCode, the ScanDate is automatically
populated,
the data is transacted to the SQL table, and the fields clear,
ready
for the next scan.

Here is the only code I have, and it is for the "GO" button":

Private Sub Button1_Click(ByVal sender As System.Object, ByVal
e As
System.EventArgs) Handles Button1.Click
Dim objConnection As New SqlClient.SqlConnection _

("server=.;database=SafetyStock;trusted_connection=true")
Dim objCommand As New SqlClient.SqlCommand("",
objconnection)
Dim objTransaction As SqlClient.SqlTransaction, strSQL As
String

Try

objConnection.Open()
objTransaction = objConnection.BeginTransaction

objCommand.Transaction = objTransaction

strSQL = "INSERT INTO ActiveSafetyStock(ScanDate,
TraceCode) " & _
"VALUES('" & txtDatetime.Text & "', '" &
txtTraceCode.Text & "')"
objCommand.CommandText = strSQL
objCommand.ExecuteNonQuery()

objTransaction.Commit()
objConnection.Close()

Catch
Button1.Text = "Failed"
objTransaction.Rollback()
objConnection.Close()

End Try
End Sub
End Class

Please HELP! :)





















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