| When OrderDetails is Zero [message #335065] |
Sun, 20 July 2008 11:40  |
justbob3377
Messages: 5
Registered: July 2008
Location: Bay Area
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Junior Member |
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Here is something I've been pining over...
Let's say you have a database with an Expense and ExpenseDetail table, respectively.
And, let's say that there are two types of data entry forms:
Form #1: Expense-level only
Form #2: Expense-level + ExpenseDetail-level
For most things (e.g. Groceries, Retail Purchases, etc), you would want to use Form #1 because you likely purchase many "Items" for a given trip to the store (i.e. "Expense").
But, for some "one-off" things (e.g. Haircut, Shoe Shine, Gas Pump Receipt) you could use Form #2 to streamline data-entry.
(Why enter an ExpenseDetail for a Haircut when you only ever get one Haircut at a time - unless you have multiple heads!!) 
Now for the question...
While such a design wouldn't break any Data Modeling Rules - as far as I know - it could cause conflicts when you query data!!
For instance, if you have a total of 10 purchases, and all 10 have Expense-level data, but only 6 have Detail-level data, then if you queried table ExpenseDetail to find "Total Expenditures" you would get incorrect results.
(If you queried "Total Purchase Amount" in table Expense, however, you would "catch" all 10 purchases and find "Total Expenditures".)
Is this a problem?
Can a person just be mindful of this when you create queries/reports, or is this a "Design Flaw"??
Just Bob
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| Re: When OrderDetails is Zero [message #335066 is a reply to message #335065] |
Sun, 20 July 2008 11:46  |
Frank
Messages: 7901
Registered: March 2000
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Senior Member |
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First off: I think you mixed up the reference to Form 1 and 2 in your grocery-haircut example.
For your question: Not 100% sure if I get your problem, but this sounds like the perfect place for an outer join.
[Edit: on second thoughts/read: I think you should enter the details for the single-item expense. If you are just thinking forms, you can add it automatically, in the background.
So I guess my answer is "yes, it looks like a design flaw"]
[Updated on: Sun, 20 July 2008 11:48] Report message to a moderator |
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| Re: When OrderDetails is Zero [message #335067 is a reply to message #335066] |
Sun, 20 July 2008 12:05 |
justbob3377
Messages: 5
Registered: July 2008
Location: Bay Area
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Junior Member |
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| Frank wrote on Sun, 20 July 2008 09:46 | First off: I think you mixed up the reference to Form 1 and 2 in your grocery-haircut example.
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Yah, you are right, I screwed that up! 
| Quote: | [Edit: on second thoughts/read: I think you should enter the details for the single-item expense. If you are just thinking forms, you can add it automatically, in the background.
So I guess my answer is "yes, it looks like a design flaw"]
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Ugh! So it is a bad design to not enter an ExpenseDetail for every Expense?
Is that for the reason I was trying to point out?
Just Bob
[EDITED by LF: fixed [quote] tags]
[Updated on: Sun, 20 July 2008 14:09] by Moderator Report message to a moderator |
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