[AccessD] Whilst on DLOOKUPs....

Darryl,

  All the Domain functions are really encapsulated SQL statements, which can
be used where an expression is allowed, but an SQL statement is not.

  Because of that, it also means they should not ever be used in a SQL
statement.  The simple reason being is that the query optimizer cannot
optimize them and since they represent an SQL statement anyway, you should
be using the appropriate Join(s) and SQL statements.

  As for them always being slower, that is not the case.  A Dlookup() for
example can be as fast as other methods.  However it is inefficient to do
something like this:

  =Dlookup("[FirstName]","tblEmployee","[EmployeeID] = " & lngEmployeeID)
  =Dlookup("[LastName]","tblEmployee","[EmployeeID] = " & lngEmployeeID)
  =Dlookup("[MiddleName]","tblEmployee","[EmployeeID] = " & lngEmployeeID)

  If your fetching anything more then a field or two, your far better off to
open a record set, fetch the record, and then have access to the entire
record.

Jim.


-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Darryl Collins
Sent: Monday, May 09, 2011 08:18 PM
To: Access Developers discussion and problem solving
Subject: [AccessD] Whilst on DLOOKUPs....


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Hi Folks,

A database I have been given to work on uses a lot of DLOOKUPs (hundreds).
Personally I don't like them much and prefer to write SELECT SQL statements
or a neat little function to get values back from a table.  I do this as
these methods are more flexible and easier to read and debug compated to
DLOOKUP.  Using recordsets to get data also seems to be as fast as using
DLOOKUP, although given the speed of today's processors I am not sure it is
something a human would notice anyway.

The DLOOKUP is a short piece of code, but harder to read, or at least I find
it harder (often because the DLOOKUP is a long string make up of variables
and often extent outside the visibile VBE window.

I recall reading somewhere that there are issues when using a lot of
DLOOKUPs, of course I could dreaming as well.

I know Allan Browne has identified some issues, these alone would make me
nervous about using DLOOKUP so I am happy not to bother with them.
<<http://allenbrowne.com/ser-42.html>>

However, curious to know what your opinion is of them.  Do I have an
attitude problem as they fast, useful and reliable or is my reluctance
worthwhile as DLOOKUP is something best to be used sparingly and with some
caution?

Cheers
Darryl.

_____________________________________

Darryl Collins | Business Analyst Database Developer
Retail Business Insurance
Insurance Australia Group (IAG)
Level 2, 181 Williams St, Melbourne, 3000 - Australia
Ph: + 61 3 9916 3926
Mobile: + 61 418 381 548



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