python sql query in django

[May]

I have three tables:

class Technology(models.Model):
technology = models.CharField(max_length=100, null=True,
blank=True )
def __unicode__(self):
return self.technology
class Meta:
ordering = ["technology"]

class Publication(models.Model):
pubtitle = models.TextField(null=True, blank=True)
def __unicode__(self):
return self.pubtitle
class Meta:
ordering = ["pubtitle"]

class Techpubcombo(models.Model):
technology = models.ForeignKey(Technology)
publication = models.ForeignKey(Publication)

The user selects a technology from the drop down menu on the web
page. The technology is retrieved
from the database table and then it must be used to retrieve the
publication attributes, by first going through the Techpubcombo table.

I wrote the select to retrieve the data for the html drop down box:
technology_list = Technology.objects.all().order_by('technology')

After the user makes a selection, the technology_id is retrieved:
technology_id = request.POST['technology_id']
t = get_object_or_404(Technology, pk=technology_id)

Now I need to use the technology_id to get to the publication
attributes

This is where I'm stuck.

I get error messages when I try to do something like:

pub=t.techpubcombo.publications_set()

Ana

 

[Bruno Desthuilliers]

May a écrit :

I have three tables:

Actually - from Python's code POV - three Model classes. And actually,
since there's a very active, friendly and helpful django group on
googlegroups, you'd be better reposting your question there.

(snip Django's ORM related question)

 

[May]

May a écrit :


Actually - from Python's code POV - three Model classes. And actually,
since there's a very active, friendly and helpful django group on
googlegroups, you'd be better reposting your question there.

(snip Django's ORM related question)

The django users groups suggests using a manytomany field. That works
well in the html template, but in the admin tables, the logic for the
manytomany field applies to the wrong model and doesn't create a
choice for the data entry people. I'm trying to write this without
using the manytomany option. Just using the standard relational
database model. I need to understand if python can do what I need to
do. So far, I've not been successful with an answer in users groups.

Ana

 

[Bruno Desthuilliers]

May a écrit :
(snip)

I may not stay with Django.

Nope, but your question was about Django.

I am seriously looking for whether python
can read data from a relational database

Of course - as long as there's a Python adapter for your DB.

and send to an html template

Of course - as long as it's either a Python templating system or there's
a Python binding for this system.

or do I always need some kind of wrapper/interface such as Rails

Uh ? Rails is a Ruby framework.

or
Django?

No, you don't. If you prefer to reinvent the wheel on each and any part
of each an any web app you write, please feel free to do so.

If this is the wrong group to ask that question

Which "that" question ?-)

For question related to Django's ORM, the django group is indeed a
better place (as usual: always use the most specific group / maling list
/ whatever first). If you have questions (like the above) that are about
Python itself, you're at the right place.

 

[Steve Holden]

The django users groups suggests using a manytomany field. That works
well in the html template, but in the admin tables, the logic for the
manytomany field applies to the wrong model and doesn't create a
choice for the data entry people. I'm trying to write this without
using the manytomany option. Just using the standard relational
database model. I need to understand if python can do what I need to
do. So far, I've not been successful with an answer in users groups.

I am sure if you explain in detail exactly what you want the admin to
present to your data entry people there are those on django-users who
can help you make it happen. That list *would* be the best place to get
an answer: this one mostly discusses the Python language in a more
generic manner.

regards
Steve

 

[May]

I am sure if you explain in detail exactly what you want the admin to
present to your data entry people there are those on django-users who
can help you make it happen. That list *would* be the best place to get
an answer: this one mostly discusses the Python language in a more
generic manner.

regards
 Steve

I may not stay with Django. I am seriously looking for whether python
can read data from a relational database and send to an html template
or do I always need some kind of wrapper/interface such as Rails or
Django? If this is the wrong group to ask that question could you
recommend another python group that could?

Thanks.

 

[Diez B. Roggisch]

I may not stay with Django. I am seriously looking for whether python

can read data from a relational database and send to an html template
or do I always need some kind of wrapper/interface such as Rails or
Django? If this is the wrong group to ask that question could you
recommend another python group that could?

Python itself comes neither with an ORM, nor with a HTML
generating/mapping framework.

So yes, if you want something like that, need something like rails or
django. Or TurboGears.

For example, you can use SQLAlchemy as ORM, and RUM as frontend for it.
I'm not sure if it fullfills your requirements though.

http://python-rum.org/

Diez

 

[Philip Semanchuk]

Python itself comes neither with an ORM, nor with a HTML generating/
mapping framework.

So yes, if you want something like that, need something like rails
or django. Or TurboGears.

For example, you can use SQLAlchemy as ORM, and RUM as frontend for
it. I'm not sure if it fullfills your requirements though.

And if you don't like ORMs, most databases have at least one adapter
out there that allows one to send straight SQL to the DB engine and
get results back in some useful form. For instance, there's the
psycopg2 adapter for talking to Postgres. Python has a built-in
wrapper for SQLite.

 

[May]

May a écrit :
(snip)


Nope, but your question was about Django.


Of course - as long as there's a Python adapter for your DB.


Of course - as long as it's either a Python templating system or there's
a Python binding for this system.


Uh ? Rails is a Ruby framework.


No, you don't. If you prefer to reinvent the wheel on each and any part
of each an any web app you write, please feel free to do so.


Which "that" question ?-)

For question related to Django's ORM, the django group is indeed a
better place (as usual: always use the most specific group / maling list
/ whatever first). If you have questions (like the above) that are about
Python itself, you're at the right place.

Thanks for all your suggestions. From what I've experienced in Django
and now that I know a little more about how Python functions, I will
probably use a combination of PHP and Django, instead of trying to get
Python to do the web portion of my project. Thanks again!

 

[Diez B. Roggisch]

Thanks for all your suggestions. From what I've experienced in Django
and now that I know a little more about how Python functions, I will
probably use a combination of PHP and Django, instead of trying to get
Python to do the web portion of my project. Thanks again!

That sounds like the worst idea. Django's ORM is good when used from
within django, because of all the additional goodies like the admin
interface.

But if you are going to do the webfrontend using PHP, what part is left
for django? If it's only the ORM (for whatever you still use that
anyway), there are better alternatives - SQLAlchemy, and SQLObject, for
Python. They are more powerful and not interwoven with django.


If you are going to hand-code the interface in PHP, I fail to see though
why you don't do that in Django directly. You are not forced to use the
Admin-interface.

Diez

 

[May]

That sounds like the worst idea. Django's ORM is good when used from
within django, because of all the additional goodies like the admin
interface.

But if you are going to do the webfrontend using PHP, what part is left
for django? If it's only the ORM (for whatever you still use that
anyway), there are better alternatives - SQLAlchemy, and SQLObject, for
Python. They are more powerful and not interwoven with django.

If you are going to hand-code the interface in PHP, I fail to see though
why you don't do that in Django directly. You are not forced to use the
Admin-interface.

Diez

Hello Diez,

I think Django is fabulous for the admin-interface, a simple text
search and template inheritance. I will use Django for all of those.
What I'm not getting an answer to and cannot find an example of is a
complex search, where I have to retrieve data from multiple tables,
combine the data, remove the duplicates, etc between a web page and
the database. The code that started this thread is only a small piece
of the complex data retrieval I need to do. PHP is great for writing
complex SQL queries right in the HTML template and I know exactly what
it is doing.

 

[Bruno Desthuilliers]

May a écrit :

Hello Diez,

I think Django is fabulous for the admin-interface, a simple text
search and template inheritance.

And I think you really don't get what Django is good for.

I will use Django for all of those.
What I'm not getting an answer to and cannot find an example of is a
complex search, where I have to retrieve data from multiple tables,
combine the data, remove the duplicates, etc

Django's ORM is mostly a wrapper above the db-api. It's intended to make
most common db access a no-brainer, not to replace full-blown SQL for
complex things. Now the good news is that you *still* can drop to a
lower raw-sql level - the one you'd get using either PHP or Python's
db-api - for more complex things. IOW, PHP won't buy you anything here.

The code that started this thread is only a small piece
of the complex data retrieval I need to do.

The "code that started this thread" is a total no-brainer using Django
(as you would know by now if you had reposted your question on django's
group - or even just read the FineManual, where this use case is fully
documented), and doesn't even require going down to raw sql.

PHP is great for writing
complex SQL queries right in the HTML template

What the .... a complex SQL query has to do in a template anyway ???
Sorry, but what you're saying here is that PHP is great for writing
unmaintainable spaghetti code. FWIW, even PHP coders are trying to get
out of this kind of mess nowadays.

 

[Diez B. Roggisch]

I think Django is fabulous for the admin-interface, a simple text

search and template inheritance. I will use Django for all of those.
What I'm not getting an answer to and cannot find an example of is a
complex search, where I have to retrieve data from multiple tables,
combine the data, remove the duplicates, etc between a web page and
the database. The code that started this thread is only a small piece
of the complex data retrieval I need to do. PHP is great for writing
complex SQL queries right in the HTML template and I know exactly what
it is doing.

First of all, mixing technologies without need is most of the times a
bad idea - so if it is really the case that you can't solve all of your
issues in django, you shouldn't use it at all, but solve them in PHP.


But to be honest - I doubt that django isn't capable of solving your
problem.

See

http://docs.djangoproject.com/en/dev/topics/db/queries/#topics-db-queries

for a introduction to the multitude of query-options. I doubt that your
rather simple m:n-relationship is covered there.


I myself use SQLAlchemy, and that can for sure query and filter those
relationships.

Diez

 

[Diez B. Roggisch]

for a introduction to the multitude of query-options. I doubt that your
rather simple m:n-relationship is covered there.

s/is/isn't/

Diez