On Thursday 07 February 2008 13:14:16 I wrote:
> On Thursday 07 February 2008 11:58:34 Oleg Broytmann wrote:
> > What do you mean by "changing dynamically"?
>
> I mean "dynamical system" where the state of the system is a function of
> time. I need a function which accepts a time variable as an input, and
> returns a state.
>
> Consider exchange-traded securities (e.g. stocks). An important attribute
> of a stock is its price. Stock trading prices are a time series of
> discrete points. Yahoo Finance, among others, persists series of prices
> and allows users to look them up by time. That's the kind of thing I'm
> talking about:
So then:
class SecurityState(SQLObject):
parent = ForeignKey('Security')
date = DateCol()
price = DecimalCol(size=10, precision=4)
class Security(SQLObject):
states = MultipleJoin('SecurityState', joinColumn='parent_id')
Why define a separate class for security? So that Security.id can be used as
a foreign key in other tables. For example:
class SecurityTransaction(SQLObject):
time = DateTimeCol()
price = DecimalCol(size=10, precision=4)
security = ForeignKey('Security')
Is there a better way of representing data like this in SQL/SQLObject?
TIA,
cs
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