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#1
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Overall Analysis
I'm sure this has been asked and aswrered but I looked for hours....ok Here
goes. So I'm building a real estate database managing condo sales and appartment rentals. I feel at the base should be solid locations info. But the budget is very little a few gs and they want lots of queries and reports so I'm kissing this keeping it simple and will surely not be able to offer 3nf. They don't want to deal with regions so only country state city tblCountries CountryID PK Auto CountryName CountryAbbrev tblProvinceOrState ProvinceOrStateID PK Auto ProvinceOrSateName ProvinceAbbrev tblCities CitiesID PK Auto CityName tblLocations LocationID PK CountryName FK lookup tblCountries ProvinceOrSateName FK lookup tblProvinceOrState CityName FK lookup tblCities The point is that all tables and forms will do lookups with combo boxes on the fields in Locations table, if doesn't exist than user puts element in either a new country state or city form so that data entry human errors can be avoided at all costs by forcing the said country or province or city to exist beforehand. As is the country provinces and cities drop down boxes are not synchronized. Looking at the concepts and I want to be certain b/c must do the same with Properties Buildings and Units. Is this the right direction?? All help most apreciated. See my other post if you want to see most of the tables Thanks again. Bernard Piette Solutions Architect http://www.BernardPiette.com 1610 Boul. St-Jospeh, Suite 1 Lachine, Quebec H8S 2N1 Tel: (514)577-7978 |
#2
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Overall Analysis
The structure you are suggest does not provide a way to specify what
states/provinces are valid for any given country. So when you select a city in your 4th table, there would be nothing to stop me choosing Las Vages, Ontario, France. Here's a simpler suggestion that identifies country, state/province + country, and city + state/province + country: tblCountry *CountryID* Text abbreviated name Country Text full name. tblState *StateID* Text abbreviated name *CountryID* Text f.k. to tblCountry.CountryID. State Text full name. tblCity *CityID* AutoNum primary key City Text StateID Text ) f.k. to tblState CountryID Text ) Primary keys are marked with asterisks. I've suggested using natural keys for the first 2 tables rather than autonumbers. An artificial key seems like unnecessary overhead to me, and this also solves the interface issue of the disappearing values when the bound column is hidden and you filter your combos. You could a natural key in the 3rd table as well: City + StateID + CountryID. That would work well, you may well *want* that combination in your related tables. However the 3-field key can start to get unweildy if you then have other tables related off that that become 4- and 5-field keys. So, while you certainly want a unique index on the combination of those 3 fields, I've suggested the artificial key as I imagine that all sales data end up relating back to the CityID at some point. HTH. -- Allen Browne - Microsoft MVP. Perth, Western Australia. Tips for Access users - http://allenbrowne.com/tips.html Reply to group, rather than allenbrowne at mvps dot org. "Bernard Piette" wrote in message ... I'm sure this has been asked and aswrered but I looked for hours....ok Here goes. So I'm building a real estate database managing condo sales and appartment rentals. I feel at the base should be solid locations info. But the budget is very little a few gs and they want lots of queries and reports so I'm kissing this keeping it simple and will surely not be able to offer 3nf. They don't want to deal with regions so only country state city tblCountries CountryID PK Auto CountryName CountryAbbrev tblProvinceOrState ProvinceOrStateID PK Auto ProvinceOrSateName ProvinceAbbrev tblCities CitiesID PK Auto CityName tblLocations LocationID PK CountryName FK lookup tblCountries ProvinceOrSateName FK lookup tblProvinceOrState CityName FK lookup tblCities The point is that all tables and forms will do lookups with combo boxes on the fields in Locations table, if doesn't exist than user puts element in either a new country state or city form so that data entry human errors can be avoided at all costs by forcing the said country or province or city to exist beforehand. As is the country provinces and cities drop down boxes are not synchronized. Looking at the concepts and I want to be certain b/c must do the same with Properties Buildings and Units. Is this the right direction?? All help most apreciated. See my other post if you want to see most of the tables Thanks again. Bernard Piette Solutions Architect http://www.BernardPiette.com 1610 Boul. St-Jospeh, Suite 1 Lachine, Quebec H8S 2N1 Tel: (514)577-7978 |
#3
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Overall Analysis
On Sat, 3 Dec 2005 11:26:26 +0800, "Allen Browne"
wrote: You could a natural key in the 3rd table as well: City + StateID + CountryID. Minor nitpick: There are two "cities" named Los Alamos in New Mexico. One's the famous one, another is a tiny dot on the map north of Las Vegas (the one in New Mexico, not the bigger one in Nevada). I'm not sure how the Post Office copes... county name maybe... g John W. Vinson[MVP] |
#4
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Overall Analysis
"John Vinson" wrote in message ... On Sat, 3 Dec 2005 11:26:26 +0800, "Allen Browne" wrote: You could a natural key in the 3rd table as well: City + StateID + CountryID. Minor nitpick: There are two "cities" named Los Alamos in New Mexico. One's the famous one, another is a tiny dot on the map north of Las Vegas (the one in New Mexico, not the bigger one in Nevada). I'm not sure how the Post Office copes... county name maybe... g John W. Vinson[MVP] John Vinson, Zip code. The USPS relies heavily on the zip code. Sincerely, Chris O. |
#5
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Overall Analysis
Thanks that is more towards the original. Going back there now :-)
-- If my answer has helped you, please sign in and answer yes to the question "Did this post answer your question?" at the bottom of the message, which adds your question and the answers to the database "Allen Browne" wrote: The structure you are suggest does not provide a way to specify what states/provinces are valid for any given country. So when you select a city in your 4th table, there would be nothing to stop me choosing Las Vages, Ontario, France. Here's a simpler suggestion that identifies country, state/province + country, and city + state/province + country: tblCountry *CountryID* Text abbreviated name Country Text full name. tblState *StateID* Text abbreviated name *CountryID* Text f.k. to tblCountry.CountryID. State Text full name. tblCity *CityID* AutoNum primary key City Text StateID Text ) f.k. to tblState CountryID Text ) Primary keys are marked with asterisks. I've suggested using natural keys for the first 2 tables rather than autonumbers. An artificial key seems like unnecessary overhead to me, and this also solves the interface issue of the disappearing values when the bound column is hidden and you filter your combos. You could a natural key in the 3rd table as well: City + StateID + CountryID. That would work well, you may well *want* that combination in your related tables. However the 3-field key can start to get unweildy if you then have other tables related off that that become 4- and 5-field keys. So, while you certainly want a unique index on the combination of those 3 fields, I've suggested the artificial key as I imagine that all sales data end up relating back to the CityID at some point. HTH. -- Allen Browne - Microsoft MVP. Perth, Western Australia. Tips for Access users - http://allenbrowne.com/tips.html Reply to group, rather than allenbrowne at mvps dot org. "Bernard Piette" wrote in message ... I'm sure this has been asked and aswrered but I looked for hours....ok Here goes. So I'm building a real estate database managing condo sales and appartment rentals. I feel at the base should be solid locations info. But the budget is very little a few gs and they want lots of queries and reports so I'm kissing this keeping it simple and will surely not be able to offer 3nf. They don't want to deal with regions so only country state city tblCountries CountryID PK Auto CountryName CountryAbbrev tblProvinceOrState ProvinceOrStateID PK Auto ProvinceOrSateName ProvinceAbbrev tblCities CitiesID PK Auto CityName tblLocations LocationID PK CountryName FK lookup tblCountries ProvinceOrSateName FK lookup tblProvinceOrState CityName FK lookup tblCities The point is that all tables and forms will do lookups with combo boxes on the fields in Locations table, if doesn't exist than user puts element in either a new country state or city form so that data entry human errors can be avoided at all costs by forcing the said country or province or city to exist beforehand. As is the country provinces and cities drop down boxes are not synchronized. Looking at the concepts and I want to be certain b/c must do the same with Properties Buildings and Units. Is this the right direction?? All help most apreciated. See my other post if you want to see most of the tables Thanks again. Bernard Piette Solutions Architect http://www.BernardPiette.com 1610 Boul. St-Jospeh, Suite 1 Lachine, Quebec H8S 2N1 Tel: (514)577-7978 |
#6
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Overall Analysis
Agreed, might as well go all the way. !
-- If my answer has helped you, please sign in and answer yes to the question "Did this post answer your question?" at the bottom of the message, which adds your question and the answers to the database "John Vinson" wrote: On Sat, 3 Dec 2005 11:26:26 +0800, "Allen Browne" wrote: You could a natural key in the 3rd table as well: City + StateID + CountryID. Minor nitpick: There are two "cities" named Los Alamos in New Mexico. One's the famous one, another is a tiny dot on the map north of Las Vegas (the one in New Mexico, not the bigger one in Nevada). I'm not sure how the Post Office copes... county name maybe... g John W. Vinson[MVP] |
#7
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Overall Analysis
you are right, I most definetely feel a need for county but client doesn't
want to go through that for their needs. Good point though. Thanks -- Bernard "Chris2" wrote: "John Vinson" wrote in message ... On Sat, 3 Dec 2005 11:26:26 +0800, "Allen Browne" wrote: You could a natural key in the 3rd table as well: City + StateID + CountryID. Minor nitpick: There are two "cities" named Los Alamos in New Mexico. One's the famous one, another is a tiny dot on the map north of Las Vegas (the one in New Mexico, not the bigger one in Nevada). I'm not sure how the Post Office copes... county name maybe... g John W. Vinson[MVP] John Vinson, Zip code. The USPS relies heavily on the zip code. Sincerely, Chris O. |
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