Drew Wutka
DWUTKA at marlow.com
Wed Oct 15 14:11:41 CDT 2003
You are right, Zip Codes could change into anything. But that applies to
everything we know. Should we make EVERY field a string? You can only code
for the present, and predicted future. The post office isn't going to
change the Zip Code system (at least not the basic 5 digits) without a
decent amount of lead/warning time. They have systems they'd have to modify
also.
Also, you are right, with today's processors, speed is not as critical. But
the question is, when faced with a factor of 1.5x to 2x faster, do you go
with the slower process, or the faster process? Isn't it better to stick
with the faster process? Why sacrifice any speed, to accomodate unknown
future variables?
Drew
-----Original Message-----
From: Heenan, Lambert [mailto:Lambert.Heenan at aig.com]
Sent: Wednesday, October 15, 2003 1:47 PM
To: 'Access Developers discussion and problem solving'
Subject: RE: [AccessD] Number vs text data type
Ah but...
one day in the future the design of zip codes (which is only ONE example of
a "number" that is not a number) could well be changed to something utterly
different that looks nothing like a number. You can't just keep adding
fields and complex put-it-all-back-together routines to reconstruct the
original string from a combination of strings and numbers. Well you can, but
it might make life miserable as "the management" make more wacky decisions.
As for searching for string vs numbers. Here are some results on a test Db I
threw together.
Using a table with 581,672 records: each record has a longint field and a
string field. The long field is populated with random long integer values,
and the string field has the string representation of its corresponding
integer field. Both fields are indexed with duplicates allowed.
The table is in an MDB file (44.9 MBytes) which is on a network drive, and
the network is running at just 10-mbit. So then I ran the following code to
search for random 'numbers' both as numbers and as strings...
Sub testSearch()
Dim n As Long
Dim s As String
Dim TextSearchStart As Single, TextSearchEnd As Single
Dim NumericSearchStart As Single, NumericSearchEnd As Single
Dim TextSearchTime As Single
Dim NumericSearchTime As Single
Dim x As Long
Dim strHits As Long
Dim intHits As Long
Dim db As Database
Dim rs As Recordset
Dim sCriteria As String
Randomize
Set rs = OpenDynaset(db, "tblHuge")
For x = 1 To 1000
With rs
n = CLng(Rnd() * 2 ^ 31)
s = CStr(n)
sCriteria = "nNumber=" & n
NumericSearchStart = Timer
.FindFirst sCriteria
intHits = intHits + Abs(CLng(Not .NoMatch))
NumericSearchEnd = Timer
NumericSearchTime = NumericSearchTime + (NumericSearchEnd -
NumericSearchStart)
sCriteria = "sText='" & s & "'"
TextSearchStart = Timer
.FindFirst sCriteria
strHits = strHits + Abs(CLng(Not .NoMatch))
TextSearchEnd = Timer
TextSearchTime = TextSearchTime + (TextSearchEnd -
TextSearchStart)
End With
Next x
rs.Close
Debug.Print "Average find times"
Debug.Print "Numbers:" & Format(NumericSearchTime / 1000,
"0.0000000000") & " Hits:" & intHits
Debug.Print "Strings:" & Format(TextSearchTime / 1000, "0.0000000000") &
" Hits:" & strHits
Set db = Nothing
Set rs = Nothing
End Sub
And here are the results of a few runs, last to first...
Average find times
Numbers:0.0020859370 Hits:0
Strings:0.0025468750 Hits:0
Average find times
Numbers:0.0023203120 Hits:0
Strings:0.0030234380 Hits:0
Average find times
Numbers:0.0023984380 Hits:0
Strings:0.0040195310 Hits:0
Average find times
Numbers:0.0029257810 Hits:0
Strings:0.0046445310 Hits:0
As you can see the random search values never generated any hits - not too
surprising considering the number of possible values in 32bit long.
The numeric search times were fairly consistent, and the string search times
steadily dropped. I assume that there is some sort of caching going on here.
But the main point is that at worst it took just about twice as long to
search for the string as it did to find the long. Not *such* as huge
performance hit considering we are talking about thousandths of a second.
There is also a fair bit or arithmetic going on between each search.
I goes without say (so why am I saying it?) that whne yo take out the
indexes on the fields the search times go though the roof (for the Long
field as well as the string one).
Lambert
> -----Original Message-----
> From: Drew Wutka [SMTP:DWUTKA at marlow.com]
> Sent: Wednesday, October 15, 2003 12:26 PM
> To: 'Access Developers discussion and problem solving'
> Subject: RE: [AccessD] Number vs text data type
>
> Ah, but you can always add fields to handle new anomalies! With the zip
> code, just add an 'extension' field. Original Number field is left intact
> (and all 'search' routines) would still work.
>
> Drew
>
> -----Original Message-----
> From: Heenan, Lambert [mailto:Lambert.Heenan at aig.com]
> Sent: Wednesday, October 15, 2003 8:38 AM
> To: 'Access Developers discussion and problem solving'
> Subject: RE: [AccessD] Number vs text data type
>
>
> This thread has been going on quite some time now, so why should I let it
> stop :-)
>
> One key issue that which has not yet been mentioned but should be
> considered
> is is there any possibility that the design / structure of the "numerical"
> identifier might change?
>
> To take the example of US Zip codes. Once upon a time there were no Zip
> codes, then along came 5 digit zips, and a little later the hyphen plus
> four
> digit extensions. This kind of change could happen at any point in time
> because at the end of the day a postal code is an *arbitrary* identifier.
> In
> other words there is no arithmetic meaning in a zip code, so it should not
> be stored as a number. You CAN store a 5 digit zip code as a Long Int, but
> you'll regret it if "the powers that be" decide to change things later on.
>
> As for searching for strings in a sorted list, while it is slower to
> compare
> a whole string with another whole string, vs. comparing numeric values, to
> search a sorted list really does not take that long as a standard binary
> chop approach is going to zero in very quickly on the target string. (If
> my
> mental arithmetic is up to it, searching for a string in a list of one
> billion (10^9) strings would require 30 comparisons at most.) In addition,
> the initial stages of the binary chop only need to compare the first
> character (or first few) in the string with the first character (or first
> few) of the target, not much slower than integer data comparisons. And
> it's
> just as simple to figure out if a target is within some range.
>
>
>
> Lambert
>
> > -----Original Message-----
> > From: Drew Wutka [SMTP:DWUTKA at marlow.com]
> > Sent: Tuesday, October 14, 2003 5:18 PM
> > To: 'Access Developers discussion and problem solving'
> > Subject: RE: [AccessD] Number vs text data type
> >
> > Yes, but if something can be stored JUST as a number, it is not only a
> > storage space issue, but a speed issue. If you took just the 5 digit
> Zip
> > code, (ignoring any extensions), and you wanted to search for addresses
> in
> > the range of 70000 to 80000, if the numbers are stored as text, the
> > processor is going to have to compare each digit of the number, because
> > it's
> > looking at ASCII (or unicode) and NOT a number. However, if it's stored
> > as
> > a number, then it's a VERY simple check to determine if it falls in that
> > range!
> >
> > Drew
> >
> > -----Original Message-----
> > From: Charlotte Foust [mailto:cfoust at infostatsystems.com]
> > Sent: Monday, October 13, 2003 10:48 AM
> > To: Access Developers discussion and problem solving
> > Subject: RE: [AccessD] Number vs text data type
> >
> >
> > Same holds true for social security numbers in the US and for telephone
> > numbers everywhere. There are good reasons NOT to use numbers for some
> > kinds of numeric data, which is probably where the argument comes from
> > in the first place, that and the old approach of squeezing everything
> > into the smallest possible datatype to shave storage bytes.
> >
> > Charlotte Foust
> >
> > -----Original Message-----
> > From: Susan Harkins [mailto:ssharkins at bellsouth.net]
> > Sent: Monday, October 13, 2003 7:32 AM
> > To: Access Developers discussion and problem solving
> > Subject: Re: [AccessD] Number vs text data type
> >
> >
> > What about Zip Codes, etc... what possible purpose would you have for
> > treating such an entry as a number?
> >
> > I'm afraid this isn't old school -- it's still very alive and with us.
> >
> > Susan H.
> >
> >
> > > That sounds like one of my co-workers who comes from the
> > > old school early-days C and COBOL programming. He makes everything
> > > text unless an actual calculation must be performed, even when that
> > > doesn't necessarily make sense in context. I believe that if its a
> > > number it should be treated as a number unless there is a very
> > > compelling reason not to, for all of the reasons given so far and
> > > probably others I haven't thought of. To me, logic tells
> > > you that if the data is numeric you should use a number
> > > data type, using text just muddies things up. As far as a
> > > number field needing "additional resources", especially
> > > for calculations, that makes no sense at all to me. Some
> > > number types may take additional storage space as compared
> > > to holding the same digit characters in a text type, and
> > > that can become an issue for DBAs when they are working
> > > under short drive space conditions. Other than, I can't
> > > think of a resource reason.
> > >
> > > Ron
> > >
> > > On Mon, 13 Oct 2003 10:42:15 -0400
> > > CYNTHIA SPELL <CSPELL at jhuccp.org> wrote:
> > > >I will, that's a good idea. What I've heard so far is
> > > >that logic tells you that if you don't need to calculate, you should
> > > >use text. And that a number data type requires additional resources
> > > >in order for the field to have the ability to do the calculating.
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