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Immediate Updates on Table

Posted on 2000-04-01
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Last Modified: 2010-05-02
I am using VB with Access in Windows NT.
How to Update Records Immediately?

I am Working with Stock Program When two user make the sales for same item. Stock goes negative.
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Question by:ackid32
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by:altena
ID: 2675985
Issue an SQL update command.

Send a SQL statement such as:

UPDATE STOCK_TABLE
    set stock_level = stock_level -100
  where stock_id = 9987

Good luck.
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vikiing earned 50 total points
ID: 2676724
If two different stations address the same product, both will think "There are 50 units of this", then one will sell 40, and the other will sell 30, leaving, in both cases the wrong value for the remaining stock.

To handle that situation, you need a semaphore which indicates when a certain record is available to use. If semaphore indicates a certain resource (in this case, the item record) is locked, then you must wait until the record is unlocked (the other application fress the record once it was updated).

Some data base managing systems handle semaphores automatically (which are intended for multi-modifying-users access); some others, simply not, and therefore, you must develope the concurrency control.


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by:ackid32
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Vikiing
im using Access as backend and how can i use semaphores
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by:darinw
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Reviewing question.

darinw
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by:darinw
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Hello everyone,

ackid32 -

When you post a question you are forming an alliance with the Experts. You present your problem, your allies try to help you solving your problem. In your alliance, you must let your allies know your strategic information so that the battle can be won favorably.

So far, your allies are loosing the war because you aren't holding up your end of the bargain. They post tactical information but you never respond. They ask for air cover and no planes show up.

As I said in one of your question posts before, you must respond to the Experts when they post a comment that contains a question for you.

If a solution is presented, by way of comment or answer, you must evaluate it and report back on your findings.

You need to bring your alliance to a close for each question by either accepting an answer or deleting the question.

Here is a list of the open questions you have:

===
[This group of questions require your input]
"How to get Uniq No for Masters?"
http://www.experts-exchange.com/jsp/qShow.jsp?ta=vbdatabases&qid=10317243 

"Anywhere Banking"
http://www.experts-exchange.com/jsp/qShow.jsp?ta=vbdatabases&qid=10597901 

"Refresh Intervel"
http://www.experts-exchange.com/jsp/qShow.jsp?ta=visualbasic&qid=10321556 

"How to detect a Hotkey"
http://www.experts-exchange.com/jsp/qShow.jsp?ta=visualbasic&qid=10366318 

===

[This one appears to have been abandoned by the Experts - if you wish I can delete it and refund your points]
"Immediate Updates on Table"
http://www.experts-exchange.com/jsp/qShow.jsp?ta=visualbasic&qid=10321222 

===

darinw
Customer Service
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by:ackid32
ID: 3680283
Comment accepted as answer
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Author Comment

by:ackid32
ID: 3680284
pls reply me
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by:vikiing
ID: 3687092
Semaphores are special indicators which handle the way a multiple-users transaction is carried over. As a rule, the own DBMS handles them, this is, the data base management system is who "serializes" concurrent transactions to execute one at a time, as if they weren't performed simultaneously.

But if your DBMS doesn't use them, then you must implement the semaphore scheme by yourself. Read some data base literature.

Thanks x the points.
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