Solved

Locking records in a multiuser environment

Posted on 2004-08-30
5
140 Views
Last Modified: 2010-05-02
hello everybody,

I am trying to create a vb appln that will be used in a multi user environment.

i have a table with fields like
1. id - number
2. name - text

i get duplicate id's when more than one user tries to update that table.

how to resolve this concurrency problem?

plz help me out.

thanks in advance
sarni
0
Comment
Question by:eskill
  • 2
  • 2
5 Comments
 
LVL 5

Expert Comment

by:KarcOrigin
ID: 11929401
Which DB you are using at the back end?
0
 
LVL 5

Expert Comment

by:KarcOrigin
ID: 11929417

In any case, A better solution is to use SELECT...FOR UPDATE to lock the selected rows. Another user cannot modify the row between the SELECT...FOR UPDATE and UPDATE. In fact, the row remains locked until the transaction ends.


Eg:

SELECT * FROM Test WHERE name = 'karc' FOR UPDATE;

UPDATE Test SET name = 'Origin' WHERE name = 'karc';

I hope it helps you.

Cheers!
0
 
LVL 5

Accepted Solution

by:
Z03niE earned 125 total points
ID: 11929443
If the id field is the primary key, the table would automatically reject duplicate value.
If you still want to make sure, if you are using MS SQL, you can create a stored procedure to handle the insert, update and delete process.
In the stored procedure, do the insert stuff inside a transaction , the transaction will lock the table temporaryly until it is committed. And also during the transaction check for duplicate value before updating the table.
Hope that help.
0
 

Author Comment

by:eskill
ID: 11929548
I am using MSAccess 2000 as the back end
0
 
LVL 5

Expert Comment

by:Z03niE
ID: 11929581
Maybe this will help.
In the field property set indexed value to Yes (No Duplicates).
0

Featured Post

Gigs: Get Your Project Delivered by an Expert

Select from freelancers specializing in everything from database administration to programming, who have proven themselves as experts in their field. Hire the best, collaborate easily, pay securely and get projects done right.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Background What I'm presenting in this article is the result of 2 conditions in my work area: We have a SQL Server production environment but no development or test environment; andWe have an MS Access front end using tables in SQL Server but we a…
You can of course define an array to hold data that is of a particular type like an array of Strings to hold customer names or an array of Doubles to hold customer sales, but what do you do if you want to coordinate that data? This article describes…
Get people started with the process of using Access VBA to control Excel using automation, Microsoft Access can control other applications. An example is the ability to programmatically talk to Excel. Using automation, an Access application can laun…
Get people started with the utilization of class modules. Class modules can be a powerful tool in Microsoft Access. They allow you to create self-contained objects that encapsulate functionality. They can easily hide the complexity of a process from…

813 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

17 Experts available now in Live!

Get 1:1 Help Now