Queries

[mmcclaf]

On Feb 26, 7:51 am, Steve Holden <st... at holdenweb.com> wrote:
> Murray wrote:
>
> [top-posting corrected]
>
>
>
> > -----Original Message-----
> > From: Gary Herron [mailto:gher... at islandtraining.com]
> > Sent: Thursday, February 26, 2009 1:46 AM
> > To: mmcclaf; python-l... at python.org
> > Subject: Re: Queries
>
> > mmcclaf wrote:
> >> I have to make  some queries for 4 tables I have. The following
> >> relations are:
>
> >> Classes(class, type, country, numGuns, bore, displacement)
> >> Ships (name, class, launched)
> >> Battles (name, date)
> >> Outcomes (ship, battle, result)
>
> >> The three queries I'm stuck on are the following:
>
> >> 1. Find the classes that have only one ship as a member of that class
> >> (not all ships are listed in the Ship table)
>
> Investigate a GROUP BY solution that selects groups having a count of 1.
>
> >> 2. Find the countries that had both battleships and battlecruisers
> >> (those fall under type in Classes)
>
> Look at EXISTS for one possible solutions.
>
> >> 3. Find those ships that "lived to fight another day"; they were
> >> damaged in one battle, but later fought in another.
>
> >From your model description I don't even see where the position and
>
> attitude of each ship is stored, so I don't think I can give you any
> help at all with this one.
>
> >> The best way for me to understand would be relational algebra for each
> >> of the statements.
>
> > Sounds like a homework assignment.    Good luck with it.
>
> > It is, however I was able to get the first 8 done, I am struggling with
> > these 3 particular ones. I have to make an SQL file based off of it,
> so this
> > seems to be a blockage in my works.
>
> Good luck with the homework. Remember to acknowledge the help you've had
> from this list (particularly your earlier issues: here you just have hints).
>
> regards
>  Steve
> --
> Steve Holden        +1 571 484 6266 +1 800 494 3119
> Holden Web LLC              http://www.holdenweb.com/

Yeppers always do. And thanks! As for the number 3 one... to know if
they were damaged would appear in "Result" of the Outcomes table