CREATE TABLE "deleteion" control

[Ruslan Zasukhin]

on 8/19/03 22:24, Andrew Sinning at andrew at learningware.com wrote:

> This next example is quite a bit more complex.  Each question can have
> an 'Info,' an 'Intro', and a 'Hint', but as data is concerned, all three
> of these things are of the type 'Info'.
> 
> In other words, in the table 'questions', the 3 fields 'infoId',
> 'introId' and 'hintId' all reference entries in the table 'info'.
> 
> //questions
> CREATE TABLE questions
> ( qId UNIQUE NOT NULL,
> infoId REFERENCES infos.infoId ON DELETE SET_NULL,
> introId REFERENCES infos.infoId ON DELETE SET_NULL,
> hintId REFERENCES infos.infoId ON DELETE SET_NULL,
> )

For ObjectPtr simply
    
        REFERENCES infos

> //infos
> CREATE TABLE infos
> ( infoId UNIQUE NOT NULL,\
> stemText varchar(1024) NOT NULL,\
> graphicId REFERENCES graphics ON DELETE SET_NULL,\
> soundId REFERENCES sounds ON DELETE SET_NULL
> )
> 
> 
> I don't think this is going to work without explicitly referencing the
> relationship, otherwise there will be ambiguity.

Absolutely correct!

And if you will try to do this, Valentina will return you error "ambiguity"

> Furthermore, I'm not sure the syntax "introId REFERENCES infos.infoId"
> is correct.

This is correct syntax for standard SQL and RDBMs.
ObjectPtr differ. It point NOT on some field, but on the whole Table.


        REFERENCES infos
 
> Any thoughts on what I'm getting at?  I hope I'm not turning this into a
> free tutorial on relational dbs.  I've just never been exposed to this
> concept.

-- 
Best regards,
Ruslan Zasukhin      [ I feel the need...the need for speed ]
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e-mail: ruslan at paradigmasoft.com
web: http://www.paradigmasoft.com

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