sybperl-l Archive

From: Michael Peppler <mpeppler at MBAY dot NET>
Subject: Re: Accessing @@rowcount global variable
Date: Jul 21 1998 4:56PM

Simon Yaminian writes:
 > 
 > > Simon Yaminian writes:
 > >  > 
 > >  > > 
 > >  > > Simon Yaminian writes:
 > >  > >  > Hello,
 > >  > >  > 
 > >  > >  >     The number of rows affected by a query is reflected in the @@rowcount
 > >  > >  > global variable. Is this variable accessible through Sybperl and if it is 
 > >  > >  > how?
 > >  > > 
 > >  > > In DBlib is DBCOUNT().
 > >  > > In CTlib it's
 > >  > > $rows = $dbh->ct_res_info(CS_ROW_COUNT);
 > >  > > 
 > >  >     I tried using the DBlib version, DBCOUNT() right after the
 > >  >  
 > >  > 	$dbh->dbsqlexec
 > >  > 
 > >  > call and it returned -1. The dbsqlexec call was issued after building
 > >  > the query as a batch of commands using multiple dbcmd calls. Is this a
 > >  > permissible scenario for using DBCOUNT()?
 > > 
 > > @@rowcount (and hence DBCOUNT()) only return valid data for a SELECT
 > > operation *after* all the rows have been processed. This is the normal 
 > > behaviour (and is the same on other SQL servers, such as Oracle).
 > > 
 > > Michael
 > > -- 
 > > Michael Peppler         -||-  Data Migrations Inc.
 > > mpeppler@datamig.com    -||-  http://www.mbay.net/~mpeppler
 > > Int. Sybase User Group  -||-  http://www.isug.com
 > > 
 > > 
 >     Thanks for your reply.
 > 
 >    I just think that it would have been much more meaningful if @@rowcount
 > was available before the rows were processed. Why? Because first of all,
 > if you are going through the rows one by one, you can keep track of the
 > total rows by merely updating a counter yourself. Second, knowing the rowcount
 > ahead of time helps in the decision making process and proper preparation in
 > processing the rows especially when dealing with large rowcounts. If you think
 > this is just an opinion, consider the following analogy.
 > 
 >    You are trying to walk from street A to street B and you also have the town's
 > map with you. However the map can not tell you how many blocks you need to walk
 > before you reach your destination unless you have finished walking and made it
 > to your destination. I wonder if that map has any significant and sensibe usage!
 > 
 >    Please take that for whatever it's worth to you, maybe I am just mistaken 
 > about the concept.


I just use the data that Sybase returns to me. The only way that I
could provide you with the @@rowcount info earlier would be to process 
all the rows in the query internally.

The Sybase server would have to do the same thing to return an
accurate @@rowcount value *before* returning the rows. This is a
serious performance issue. Please read the documentation on DBCOUNT()
and/or ct_res_info() in the Sybase OpenClient manuals for more info
behind this issue.

Michael
-- 
Michael Peppler         -||-  Data Migrations Inc.
mpeppler@datamig.com    -||-  http://www.mbay.net/~mpeppler
Int. Sybase User Group  -||-  http://www.isug.com