Table structure?

[Joakim Schramm]

> -----Original Message-----
> From: valentina-bounces at lists.macserve.net 
> [mailto:valentina-bounces at lists.macserve.net] On Behalf Of 
> Ruslan Zasukhin
> Sent: 28 April 2006 23:55
> To: valentina at lists.macserve.net
> Subject: Re: Table structure?
> 
> On 4/28/06 11:31 PM, "Joakim Schramm" <joakim at astrocalc.com> wrote:
> 
> For info: am I right that in your old app you have not use 
> SQL and are used to just API access to a database ?
> 
Yes basically, I am doing a concept replying other mail, and important part
I forgot about one thing, it's 3 tables. Just a minute...

Joakim
> --------------------
> > This is an "Atlas" database (none graphical, just data) so I have 
> > following, in a relational schema:
> > 
> > Table1 (A place in the world)
> > 
> Place|LatDeg|LatMin|LatSec|LatCompass|LongDeg|LogMin|LongSec|L
> ongCompass|Cou
> > ntry|TimeZoneID
> > 
> > Table2 (Timezones in the world)
> > DateTimeOfChange|ChangeVal|Ptr_Country|Ptr_TimeZoneID
> 
> > How it works in practice in program is, a place are picked, either 
> > from returned SearchCollection or from List.
> 
> Ok. So you have one select place, i.e. RECORD of T1.
> You know its RecID.
> 
> > Next, based on country AND ZoneID (most countries have just 
> 1 but some 
> > have over 300)
> 
> One country have 300 time zones?
> 
> Dummy question, isn't we have only 24 zones on earth?
> 
> > a timezone value are returned with passed DateTime as criteria.
> 
> Okay, so ONE record in T1 is "linked" to some set of records 
> in T2 But condition based on 2 fields.
> 
> > Quite simple yes in Relational,
> 
> > but I like to learn and use something new and is still 
> unfamilar with 
> > Valentina. My way of thinking though is if I learn and understand 
> > something difficult, then I understand everything, sort of...
> 
> Okay, lets try.
> 
> Look on T2.
> 
> Table2 (Timezones in the world)
>    DateTimeOfChange
>    ChangeVal
>         Ptr_Country             <<<<<<<<
>         Ptr_TimeZoneID          <<<<<<<<
> 
> 
> The last 2 fields present here ONLY BECAUSE  you need 
> establish link to T1.
> Am I right ?
> 
> Remember pictures from Valentina WIKI about links?
> In Relational model Tables have USEFUL fields and 
> UTILITY/HELPER fields.
> 
> Am I right that this is enough for T2 to bring USEFUL info:
> 
> Table2 (Timezones in the world)
>    DateTimeOfChange
>    ChangeVal
> 
> I think enough. Then be happy. Just only you have win again a 
> lots of disk space 
>         Ptr_Country            VarChar?  Avg 7 bytes
>         Ptr_TimeZoneID         Ulong ?   4 bytes
>     
>         (7 + 4 = 11) + (11 * 1.5 = 16) = 27 bytes.
> 
>         13MB of garbage, go out from my disk!!  :-)
> 
> Aha, and now question how to link records of T1 and T2?
> Answer - using Binary Link.
> 
> How to build it? Easy:
> At first build table as you have, then write special function 
> to iterate records and build BinaryLink records. Then DROP 
> that 2 fields. You do not
> need any more.    
> 
> 
> P.S. Also it seems good idea to me to extract separate table COUNTRY,
>     and put into your T1 only ObjectPtr to it.
> 
> 
> --
> Best regards,
> 
> Ruslan Zasukhin
> VP Engineering and New Technology
> Paradigma Software, Inc
> 
> Valentina - Joining Worlds of Information http://www.paradigmasoft.com
> 
> [I feel the need: the need for speed]
> 
> 
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