I'm actually i deep doubts with this. Price is not a thing itself, good point. But in my case, it was the best way i found out to model.
Suppose you got a company the rents a place (just a big room, or a party house) for any kinda envents you'd to make. The company is clear an entity, and the price would probably be its attribut, despite the following problem: This company charges diferent prices depending on the kind of party you'd like to make on its party House. You might have a company that charges you the following. - Wedding party U$100 - Under Graduation party (prom) U$200 - high school grad party (hs prom) U$ 300 Beyond that, there are the ordinary companies that have only one basic price for any kind of party (they don't change their prices depending on the parties). That's why i decided to model it as an entity, but i'm not sure in two aspects. - Should i have a M:N or a 1:N relation between these entities (note that this is actually not that trivial, maybe modelled both ways) - Should i just have a column in my price entity to specify the kinda party (like PARTY_TYPE) or just have 3 or more specific columns for the party type (lik PRICE_WEDDING, PRICE_GRADUATION, PRICE_HIGH_SCHOOL). Well, that's it ... If u could give an advise... Thanks in advance, ltcmelo --- Robert J Taylor <[EMAIL PROTECTED]> escreveu: > Leandro Melo wrote: > > >Hi, > >i have a M:N relationship between PRODUCT and > PRICE. > > > > > Is Price an Entity or an Attribute? I'm not > accustomed to using price as > a Thing. What is it that causes a Product to have > one, exactly, or more > prices? Is it its relationship to some other thing? > Or is it a special > kind of Product? > > Except during a couple years under US President > Nixon, Prices are > usually not things in themselves... can you flesh > out what you are > trying to model a little more? > > >1 product may be associated to N prices and 1 > prices > >may belong to N products. > >I got special cases the some kinda product MUST > have > >only 1 price associated with it. > >I don't what would be the best way to model this > >"flag" for the special case. > >So far, i got 3 tables. > > - PRODUCT (PRODUCT_ID as PK) > > - PRICE (PRICE_ID as PK) > > - PRODUCT_PRICE (with fields PRODUCT_ID and > PRICE_ID) > > > >Where should i put this "flg" or should tie the > >relations??? > > > > > > > Let's see what relationship to a another entity or > classifying attribute > of Product might invoke the rule on one-and-only-one > or M:N. Then we'll > know how better to proceed. > > >Thanks, > >ltcmelo > > > >______________________________________________________________________ > > > > > > > > HTH, > > Robert Taylor > [EMAIL PROTECTED] > > begin:vcard > fn:Robert Taylor > n:Taylor;Robert > adr;dom:;;9 Via Latigo;Rancho Santa > Margarita;CA;92688 > email;internet:[EMAIL PROTECTED] > tel;work:949 677 0321 > tel;cell:949 677 0321 > x-mozilla-html:FALSE > url:http://rjamestaylor.com > version:2.1 > end:vcard > > ______________________________________________________________________ Yahoo! Messenger - Fale com seus amigos online. Instale agora! http://br.download.yahoo.com/messenger/ -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
