Sybase and MS-SQL have a datatype called "timestamp" (which isn't time related at all) that can be used for this. It is an 8 byte binary column that gets updated each time the row is updated, so you can easily check if the data that the user has been editing was changed when applying the update. This is essentially the same as keeping track of changes with a counter, but happens automatically (and the timestamp column can't be modified manually).

The alternative is as others have suggested to implement your own locking mechanism via a secondary table. Be sure to include a time when the lock was acquired so that you can force the release of stale locks.

Michael

In reply to Re: Concurrency control in web applications by mpeppler
in thread Concurrency control in web applications by cbraga

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.