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#11
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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
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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
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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
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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
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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
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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] |
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