[Haskell-cafe] ORM for haskell?

Marc Weber marco-oweber at gmx.de
Tue Jun 30 18:14:34 EDT 2009

Hi Mads!

On Tue, Jun 30, 2009 at 11:49:40PM +0200, Mads Lindstrøm wrote:
> Hi Marc Weber
> > Another example: Updating the age of a pupil:
> > 
> >   row = SELECT * FROM pupils where age = 13;
> >   UPDATE pupils SET age = 14 WHERE id = <the id you got above>
> > 
> >   p = session.query(Pupil).filter(Pupil.age==13).one().age=14
> >   session.commit()
> > 
> >   difference?
> >   You don't have to care about ids. you just assign a new value and
> > tell
> >   the engine that it should commit.
> >   So again less chances to get something wrong.
> > 
> Could you not do in SQL:
> UPDATE pupils SET age = 14 WHERE age = 13
Of course.
But: you can pass around that pupil object to another function and still assign a new age
then run session.commit().
When passing around the pupile you can follow the relation_ships
(relations?) back to school.

def doSomething(pupil):
  pupil['age'] = 13
  pupil.teacher.school.rating += 1


Now how would you do this using SQL?

Sorry about the confustion (relation / relation-ship). I mixed up the terminology.
Anyway I guess you can see here how powerful an ORM can be and why
we should write such a library for haskell.

I think it's very hard to invent such a short synax in haskell cause
you have to take monads into account etc..

And it matters how much time you have to spend writing code.

Thanks for your feedback. I hope there will be some more.

Marc Weber

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