When you do the update you would have to include all the modifiable columns
in the where clause for the update statement.
IF you have cols A, B, C, D, E & F
and lets say only A B & C are updateable by any user.
then you would select a,b,c,d,e,f from table
the user would make the changes to columns(corresponding gui controls on the
webpage(s)) then you would have to fire the update statement.
update <set values>
from table
where a = <original retrieve value of a>
and b = <original retrieve value of b>
and c = <original retrieve value of c>
consider this scenario where
User 1 retirieves a record from the database at lets say 3pm
User 2 retrieves the same record at 3:05 pm
User 2 updates the record at 3:10 pm
User 1 tries to update at 3:12 pm
Now if User 1 hits the update button(and fires the above update statement
the update will fail(ie. will not affect any rows) as the original values
retrieved by user 1 have already been changed by user 2.
HTH
Sanjay
-----Original Message-----
From: Chee Keong [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, August 17, 1999 12:09 AM
To: [EMAIL PROTECTED]
Subject: Re: Database locking in multiple page Web application
Thank you for your response.
Assume that I use Oracle or Informix which supports
SELECT FOR UPDATE. However, I am still not sure how it would work
across multiple web pages the the JDBC connection would be closed.
The user would update the data on Page A and click a "Next Page Info"
link. The user would then proceed to update data on page B., etc
Finally, the use clicks Update . How can I prevent other users to
be able to select the same record for update at the same time ?
As I understand it, I would load the JDBC driver, connect to the
database , perform some SQL statements and close off the connection
withing the same JSP or servlet.
Is the record still locked although my JDBC connection is closed and
can I update this record in another JSP or servlet ?
Regards,
Chee Keong.
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