Path: utzoo!utgpu!cunews!bnrgate!brchh104!n5pph007!rap
From: rap@n5pph007.uucp (Allen Pippin,RTP,8189,)
Newsgroups: comp.databases
Subject: Re: how to implement cursor based UPDATE/DELETE
Summary: Cursor UPDATE/DELETE
Message-ID: <2865@brchh104.bnr.ca>
Date: 15 May 91 19:32:47 GMT
References: <22637@shlump.lkg.dec.com>
Sender: news@brchh104.bnr.ca
Lines: 19


Many relational managers make use of a "full" scan of some 
sort.  For example SQL/DS has the dreaded "dbspace scan", DB2 and
Oracle have the tablespace scan.  These functions make a complete pass
over all data in the table applying update/delete to those rows which match
the predicate.   In fact, in certain cases the query optimizers for
SQL/DS, DB2, and Oracle will pass up the use of an index an use the
full scan method to reduce total I/O to satisfy a request.  

By the way, the ROWID concept is in every RDBMS I am aware of, but it is
often hidden and cannot be accessed via the SQL language. 

Hope this helps...


------------------------------------------------------------------------------
Allen Pippin                               | Reply to: 
Dept 1165, Northern Telecom, Inc.          |   rap%n5pph007@rti.rti.org
RTP NC, 27709                              |