Re: Normal Form-Second(Mr.Vinson?)

Thank you so much,

this eases my task considerably. You're right a vessel only works one route
at a time, :-) (that's so funny) I think I'm so spread***-minded, that
when I tried to force myself to stop thinking that way I overdid it.

Thanks again
Mary


"Lynn Trapp" wrote:

> You are very much on the right track, but I want to try to verify a few
> things.
>
> > I got the impression that I should be minimizing my tables even more than
> > I
> > already am. Each table = 1 idea basically. So 1 idea does not
> > necessarily
> > mean only 1 attribute. My fleet roster needs to incorporate all related
> > attributes relative to all vessels(they all have
> > length,breadth,beam,name,class,colorscheme,etc) & that change rarely if at
> > all..??..
>
> Yes, each table should store the date regarding a single type of entity --
> i.e. vessels. Each field in each table should store a single, or atomic,
> value for each attribute. This is not so much about whether or not a given
> attribute will change, but whether or not it is a single attribute. When you
> need multiple attributes that, essentially, describe the same thing -- i.e.
> Route1, Route2, Route3,...RouteX, then you need a child table to store each
> instance of a route that may be related to a vessel. Of course, if a boat is
> only on one Route at any given time -- which seems likely to me -- then it's
> only a matter of changing the Route attribute when needed and that wouldn't
> require a different table, necessarily.
>
> > I use VesselID as key in Vessel/Route table as well as PKey in
> > Vessel/Equipment tables. I hope I have this right now.
>
> If VesselID is the primary key in each of the sub tables, then you will only
> be able to have one record per each record in the Vessels table. If a vessel
> requires multiple equipment values, then your table might look like this.
>
> tblVesselEquipment
> VesselEquipmentID (PK)
> VesselID (FK)
> .....other fields related to a piece of equipment.
>
> --
> Lynn Trapp
> MS Access MVP
> www.ltcomputerdesigns.com
> Access Security: www.ltcomputerdesigns.com/Security.htm
> Jeff Conrad's Big List: www.ltcomputerdesigns.com/JCReferences.html
>
>
> "FerryMary" <FerryMary@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
> news:4987BA0F-A075-43AC-87B9-FD57B1BD4029@xxxxxxxxxxxxxxxx
> > Lynn,
> >
> > Thanks, I must still be interpreting some of what I'm reading incorrectly.
> > At this link
> >
> > http://support.microsoft.com/?id=283878
> >
> > I got the impression that I should be minimizing my tables even more than
> > I
> > already am. Each table = 1 idea basically. So 1 idea does not
> > necessarily
> > mean only 1 attribute. My fleet roster needs to incorporate all related
> > attributes relative to all vessels(they all have
> > length,breadth,beam,name,class,colorscheme,etc) & that change rarely if at
> > all..??..So Class is back in(it might change 1 once in 30 years) Route
> > stays
> > out (we move boats around like checkers)
> >
> > I use VesselID as key in Vessel/Route table as well as PKey in
> > Vessel/Equipment tables. I hope I have this right now.
> >
> > TBMary
> >
> > "Lynn Trapp" wrote:
> >
> >> Mary,
> >> It looks a bit like what you are trying to do is create some sub-classing
> >> tables, when what you MAY have wanted are child tables.
> >>
> >> > tblFleetClass
> >> > VesselID
> >> > Class
> >>
> >> Will a vessel ALWAYS have a class? Will a vessel ALWAYS have only one
> >> class?
> >> If the answer to both of those questions is 'yes', then I would leave the
> >> class field in tblFleet and not have this table.
> >>
> >> > tblFleetRoute
> >> > VesselID
> >> > Route
> >>
> >> Will a vessel always only have one route? Is VesselID the primary key of
> >> this table? If it is, then you can only have one route per vessel. The
> >> same
> >> situation might apply here as to tblFleetClass.
> >>
> >> --
> >> Lynn Trapp
> >> MS Access MVP
> >> www.ltcomputerdesigns.com
> >> Access Security: www.ltcomputerdesigns.com/Security.htm
> >> Jeff Conrad's Big List: www.ltcomputerdesigns.com/JCReferences.html
> >>
> >>
> >>
>
>
>
.