A Microsoft Office (Excel, Word) forum. OfficeFrustration

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » OfficeFrustration forum » Microsoft Access » Database Design
Site Map Home Register Authors List Search Today's Posts Mark Forums Read  

Tables and relationships?



 
 
Thread Tools Display Modes
  #11  
Old January 19th, 2010, 05:26 AM posted to microsoft.public.access.tablesdbdesign
Tom van Stiphout[_2_]
external usenet poster
 
Posts: 1,653
Default Tables and relationships?

On Sun, 17 Jan 2010 18:34:01 -0800, awsmitty
wrote:

Indeed, you can do this and much more once you have an efficient
database design. And believe it or not, for the most part all database
designers agree on what that structure should be, given a set of
requirements. The field names may be different, but you will see very
similar structures. This is because relational database design is
firmly rooted in the mathematics of set theory and a rookie developer
cannot just come around and proclaim that math does not apply to
him/her.
Once this approach clicks for you, you will see more and more
advantages. And you can always come back here and ask more questions.
They will be A LOT easier to answer if you have a correct design.

-Tom.
Microsoft Access MVP



clip
Now that table may need to be searchable. John makes a donation, files his
taxes, but two years later the IRS comes along and questions it. In the
meantime John has lost his receipt. John, or for that matter the IRS might
come to us to verify that John donated all this stuff. I can find John
easily enough, just give me his address and I’ll use the same routine as when
I found him the first time. I assume what Tom was trying to do, and what I’m
interested in doing just as an educational exersize, is to manage the data
efficiently and conveniently, and learn a little along the way. I assume
Tom’s method would be more efficient. Convenient, well, for you guys that
know this forwards and backward, maybe so, but for me, I have to really keep
my eye on the ball or I’ll loose track of what’s gong on. But, it could
prove to be interesting.

  #12  
Old January 19th, 2010, 03:41 PM posted to microsoft.public.access.tablesdbdesign
Fred
external usenet poster
 
Posts: 1,451
Default Tables and relationships?

I my case it was just agreeing with y'all said, but viewing/explaining such
it in a different way.

I believe that it more useful to look at a "junction table" as just another
table that records entities. In this case, the entity is instances of a an
item type being donated. In this case I think that such is not only an
entity, but it the main entity that they are recording.


  #13  
Old January 19th, 2010, 06:10 PM posted to microsoft.public.access.tablesdbdesign
Jeff Boyce
external usenet poster
 
Posts: 8,621
Default Tables and relationships?

Tom

As an alternative to Single, do you find it useful to use the "Currency"
data type?

Regards

Jeff Boyce
Microsoft Access MVP

--
Disclaimer: This author may have received products and services mentioned
in this post. Mention and/or description of a product or service herein
does not constitute endorsement thereof.

Any code or pseudocode included in this post is offered "as is", with no
guarantee as to suitability.

You can thank the FTC of the USA for making this disclaimer
possible/necessary.

"Tom van Stiphout" wrote in message
...
On Sun, 17 Jan 2010 13:39:01 -0800, awsmitty
wrote:

I mean that this table will have a field named Quantity, which is of
datatype Single, and it is a required field.
This will allow you to record how many items of a particular kind
there were in one particular donation. I first thought to use Integer
for the data type, but what if someone donated $12.50? Maybe your item
is "money", and your quantity is 12.5.

-Tom.
Microsoft Access MVP



Tom.
At the end of the forth paragraph, you mention"quantity single required".
I
have to ask, what do you mean?



  #14  
Old January 20th, 2010, 03:31 AM posted to microsoft.public.access.tablesdbdesign
Tom van Stiphout[_2_]
external usenet poster
 
Posts: 1,653
Default Tables and relationships?

On Tue, 19 Jan 2010 09:10:35 -0800, "Jeff Boyce"
wrote:

Usually yes, I am a big proponent of using the smallest and most
accurate data type. But I think this is a justifyable exception: we
want only a single Quantity field, and it can hold the number of beds
donated, or gallons of drinking water, or yards of linnen, etc.

-Tom.
Microsoft Access MVP


Tom

As an alternative to Single, do you find it useful to use the "Currency"
data type?

Regards

Jeff Boyce
Microsoft Access MVP

  #15  
Old January 20th, 2010, 05:59 PM posted to microsoft.public.access.tablesdbdesign
Jeff Boyce
external usenet poster
 
Posts: 8,621
Default Tables and relationships?

Tom

I misunderstood. I thought the "Single" data type was one that offered
considerably more precision than "Currency".

Regards

Jeff

"Tom van Stiphout" wrote in message
...
On Tue, 19 Jan 2010 09:10:35 -0800, "Jeff Boyce"
wrote:

Usually yes, I am a big proponent of using the smallest and most
accurate data type. But I think this is a justifyable exception: we
want only a single Quantity field, and it can hold the number of beds
donated, or gallons of drinking water, or yards of linnen, etc.

-Tom.
Microsoft Access MVP


Tom

As an alternative to Single, do you find it useful to use the "Currency"
data type?

Regards

Jeff Boyce
Microsoft Access MVP



  #16  
Old January 20th, 2010, 07:22 PM posted to microsoft.public.access.tablesdbdesign
John W. Vinson
external usenet poster
 
Posts: 18,261
Default Tables and relationships?

On Wed, 20 Jan 2010 08:59:44 -0800, "Jeff Boyce"
wrote:

Tom

I misunderstood. I thought the "Single" data type was one that offered
considerably more precision than "Currency".


Well... apples and oranges.

Single is a 16-bit floating point number, which provides approximately 7
digits of precision, with an exponent numbers up to about 10^37. So you could
have 12345670000000000 but it would be indistinguishable from
12345670100000000 (because the 1 is lost in the roundoff error).

Currency is a scaled huge integer, with exactly four decimal places and a
range into the trillions. It doesn't have roundoff error but you can't store
10^37 in it either.
--

John W. Vinson [MVP]
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Forum Jump


All times are GMT +1. The time now is 08:38 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 OfficeFrustration.
The comments are property of their posters.