Depends on what .db you are using.
Oracle has SQL extensions that allow you to specify exactly which rows of a
query to return i.e. between 100 and 200 (I forget the exact syntax).
SQL Server + others only allow you to do the TOP x rows.
>From your mail I assume you not using Oracle.
Two database solutions. Assuming you want rows X to X + n
Write an SP that does a query for TOP (X + n) rows, opens a cursor on the
result set and navigates through the cursor returning the required rows.
Write out the entire query to a temporary table with a query ID and
sequential row id's. You can then query the table for the required page.
Obviously you need to store the current page number (in the session context
or a statefull session bean ?).
Hope this helps,
Matt.
> -----Original Message-----
> From: Gary Windham [mailto:[EMAIL PROTECTED]]
> Sent: Friday, July 28, 2000 8:02 PM
> To: [EMAIL PROTECTED]
> Subject: Re: Statefull session bean to handle queries
>
>
> This is an interesting problem that I've been wrestling with
> in the context
> of master-detail lists. I have a "master list view" in our
> application that
> is implemented as pages, which can be navigated sequentially
> or randomly.
> My current approach is to use a stateless session bean which
> performs a JDBC
> query using a "SELECT TOP ..." statement and then cursoring
> through the
> resultset (e.g., if a page size is 20 rows, and you want the
> 5th page, you
> use a "TOP 100", then cursor down 80 rows). Obviously this
> approach is
> fraught with problems. I haven't been able to find an
> approach that is a
> complete "win". Stateful session beans have scalability and resource
> consumption problems. One approach that I've been
> investigating is using
> "transient entity beans", which live only in the EJB object cache (see
> http://www.c2.com/cgi/wiki?SearchResultAsEntityBean and
> http://www.c2.com/cgi/wiki?TransientEntityBean). The risk
> here is that if
> you have a large result set, and/or lots of client "think
> time" between
> "chunk" retrievals, your entity bean could be flushed from
> the cache before
> you're done with it...in which case you would have to
> re-execute your query.
>
> --Gary
>
> -----Original Message-----
> From: A mailing list for Enterprise JavaBeans development
> [mailto:[EMAIL PROTECTED]]On Behalf Of Chris Brown
> Sent: Friday, July 28, 2000 8:50 AM
> To: [EMAIL PROTECTED]
> Subject: Statefull session bean to handle queries
>
>
> Has anyone had success with or have suggestions on the following?
>
> Use a statefull session bean to handle queries from a client
> (servlet). The
> statefull session bean will create and hold on to the
> resultset on behalf of
> the client. The client controls the display of "result
> pages" to the user
> and calls methods on the statefull session bean to move through the
> resultset. The results are passed back to the client as a
> collection of
> "state" objects. The servlet will store a handle to the
> session bean in the
> session.
>
> Concerns:
> Is this the proper design?
> How long is the statefull session bean tied to the client?
> Passivate/Activate - will the resultset be
> serialized/deserialized properly?
> Can it handle large result sets? 20,000+ rows?
>
> Thanks in advance,
> Chris
>
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