Asger Blond
ab-mi at post3.tele.dk
Sat Jun 4 04:15:37 CDT 2011
Certainly not (c)! I was the dumb one suggesting that rst.index is creating a temporary index - in fact it is invoking an already created index. As to (a) and (b) I don't know - maybe some other? Asger -----Oprindelig meddelelse----- Fra: accessd-bounces at databaseadvisors.com [mailto:accessd-bounces at databaseadvisors.com] På vegne af William Benson Sendt: 4. juni 2011 05:28 Til: Access Developers discussion and problem solving Emne: Re: [AccessD] Most efficient means to retrieve most recent record Hey... I am new to this. What I wonder is if in a procedure where I was setting a recordset equal to a whole table then maybe that rst can be declared publicly in which case that index lasts pretty much my whole session once it is called, unless it is ret to nothing? Or would that (a) lock up my table so it couldn't be used or ( b) slow down my database or (c) be too dumb for you to even comment on? ;) Bill Benson Ownet VBACreations, LLC On Jun 3, 2011 8:09 PM, "Asger Blond" <ab-mi at post3.tele.dk> wrote: > William, > And help me too understand something ;-) > Isn't rst.index just creating a *temporary* index which would have to be recreated each time you execute your procedure? Frankly I don't know - but why not create an ordinary once-and-for-all index which could then be used by every subsequent queries whether on a recordset or in a plain sql? > Asger > > -----Oprindelig meddelelse----- > Fra: accessd-bounces at databaseadvisors.com [mailto: accessd-bounces at databaseadvisors.com] På vegne af William Benson (VBACreations.Com) > Sendt: 4. juni 2011 00:40 > Til: 'Access Developers discussion and problem solving' > Emne: Re: [AccessD] Most efficient means to retrieve most recent record > > Help me understand something please: Wasn't the tenor of a previous post > that opening a table-type recordset is not really the same thing as trying > to hold the entire table in memory -- that it is not until one actually > scans the table that the database experiences a performance impact? > > If I inferred badly, then nevermind my next question... > > If what I inferred is correct, then here is a follow-up: If the table-type > recordset has the index method implemented using Rst.Index "ixwhatever", and > one uses SEEK, how is that any slower than implementing the Select TOP 1 > statement within the SQL at the time a recordset is opened? In the former > case, one is ultimately SEEKing on an indexed entity. In the latter, one is > executing an SQL statement on a (slow) data source. > > I would follow THAT question up with another... is there a difference here > when we're talking one-offs versus repeated SEEKs. In other words, perhaps > implementing .INDEX is slow, but it will be more than made up for by the > fact that each SEEK statement will then be many times faster, whereas > repeated executions of a dynaset recordset against a non-indexed table will > ultimately fall behind in performance? > > Thanks. > > > -----Original Message----- > From: Stuart McLachlan > Sent: Saturday, June 04, 2011 9:31 AM > To: Access Developers discussion and problem solving > Subject: Re: [AccessD] Most efficient means to retrieve most recent record > > I think you will find that SELECT TOP 1..... will use SEEK under the hood > and it has got to be faster just retrieving one record than retrieving a > potentially large recordset and then using SEEK on it in code. > > > -- > Stuart > On 3 Jun 2011 at 15:05, Jim Dettman wrote: > > > -- > AccessD mailing list > AccessD at databaseadvisors.com > http://databaseadvisors.com/mailman/listinfo/accessd > Website: http://www.databaseadvisors.com > > > -- > AccessD mailing list > AccessD at databaseadvisors.com > http://databaseadvisors.com/mailman/listinfo/accessd > Website: http://www.databaseadvisors.com -- AccessD mailing list AccessD at databaseadvisors.com http://databaseadvisors.com/mailman/listinfo/accessd Website: http://www.databaseadvisors.com