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Posted by DaveP on 03/14/07 20:11
Im Confused about ur tables
movies MovieId(identity), other columns, DirectorId (from Directors),
genresId (from Genres)
if your table is not designd somewhat like the above, gonna be hard to link
the child tables(ref tables, directors, genres)
movie
movieid (identy)
title
genres (id from genres) could be identy in genres or another unique id
director (id from Director) could be identy in genres or another unique id
yearmade
Studio
etc
hope the above helps
DaveP
"Ed Murphy" <emurphy42@socal.rr.com> wrote in message
news:45f59e2c$0$16735$4c368faf@roadrunner.com...
> Dot Net Daddy wrote:
>
>> I have set up a database for movies. In one table (Movies) I have
>> movie names, and production years, and also genres. In another table
>> (Directors), I keep the directors and the movies they directed.
>
> Based on your query, I assume that you are /not/ making the classic
> violation of 1NF, which would look like:
>
> ID | ListOfMovieIDs
> ---+---------------
> 1 | 1,2
> 2 | 3
> 3 | 3
>
> but rather you have done it correctly:
>
> ID | MovieID
> ---+--------
> 1 | 1
> 1 | 2
> 2 | 3
> 3 | 3
>
> Personally, I would rename the ID column to DirectorID. In particular,
> some tools (e.g. the Smart Linking option in Crystal Reports) will give
> more useful results if you do this. Similarly for the ID columns in
> the other tables.
>
>> Another table (People) keeps the names of the people. Everybody will
>> have a unique ID. I have created a query like below to show the name
>> and production year of the movie, the director name and the genre of
>> the movie. Genres are also defined in a tabled called Genres.
>>
>> SELECT Movies.Name, Movies.Year, People.Name AS Director, Genres.Genre
>> FROM Movies INNER JOIN Directors ON Movies.ID = Directors.MovieID
>> INNER JOIN Genres ON Movies.Genre = Genres.ID INNER JOIN People ON
>> Directors.ID = People.ID WHERE (Movies.ID = @MoviesID)
>>
>>
>> The problem is that it does not return any result. What might be the
>> problem?
>
> Build up the query one level at a time:
>
> SELECT Movies.Name, Movies.Year
> FROM Movies
> WHERE Movies.ID = @MoviesID
>
> If this returns zero rows, then @MoviesID is not in the Movies table.
>
> SELECT Movies.Name, Movies.Year, Director.ID as DirectorID
> FROM Movies
> INNER JOIN Directors ON Movies.ID = Directors.MovieID
> WHERE Movies.ID = @MoviesID
>
> If this returns zero rows, then Movies.ID is not in the Directors
> table.
>
> SELECT Movies.Name, Movies.Year, People.Name as Director
> FROM Movies
> INNER JOIN Directors ON Movies.ID = Directors.MovieID
> INNER JOIN People ON Directors.ID = People.ID
> WHERE Movies.ID = @MoviesID
>
> If this returns zero rows, then Directors.ID is not in the People
> table. Fix all such cases, then add a foreign-key constraint to
> prevent it from happening again.
>
> SELECT Movies.Name, Movies.Year, People.Name as Director, Genres.Genre
> FROM Movies
> INNER JOIN Directors ON Movies.ID = Directors.MovieID
> INNER JOIN People ON Directors.ID = People.ID
> INNER JOIN Genres ON Movies.Genre = Genres.ID
> WHERE Movies.ID = @MoviesID
>
> If this returns zero rows, then Movies.Genre is not in the Genres
> table. Fix and add constraint.
>
> Alternatively, you can replace any/all of the INNER JOINs with
> LEFT OUTER JOINs. You will then get NULLs from that branch of
> the join tree, e.g. if Movies.ID is not in the Directors table
> then anything you attempt to get from Directors *or* People will
> be NULL. COALESCE(SomeField,'DefaultValue') may be of interest.
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