Simple Join with no matching primary keys

[aysh...@gmail.com]

Greetings,

I am trying to do a join on the following 2 models (tables)

class Rio1(models.Model):
    datestr = models.DateTimeField()
    source = models.TextField()
    dFlag = models.TextField()
    url = models.TextField()

    class Meta:
        managed = False
        db_table = 'rio1'

class Rio2(models.Model):
    datestr = models.DateTimeField()
    source = models.TextField()
    dFlag = models.TextField()
    url = models.TextField()

    class Meta:
        managed = False
        db_table = 'rio2'

In each table there is a primary ID column, but it does not have the same values in both tables, only datestr and source are the identical, now the trick is that both datestr and source are appearing 4 times per every single day, hence I can't set datestr or source to be unique primary keys. 

When I did a simple dummy join, the Django query yields no results because it is joing on the ID column which is of course won't bring back any matched records from the two tables. What would be the correct way to join such tables?

Many thanks!

[Melvyn Sopacua]

On Tuesday 07 March 2017 10:50:24 aysh...@gmail.com wrote:

> Greetings,

>

> I am trying to do a join on the following 2 models (tables)

 

Models cannot be joined. There is no Model.join(). Models are objects you can relate to eachother.

Once you stop thinking in database terms, the problem is easily solved.

 

Since the two models are identical, why would you use two models? Your problem starts with your design - rethink it.

--

Melvyn Sopacua

[aysh...@gmail.com]

Thanks for your answer, the models represent two different tables, identical structure but have to be segregated, there is no better design options to implement them. Any leads on how to do the join?

[Melvyn Sopacua]

On Wednesday 08 March 2017 06:23:44 aysh...@gmail.com wrote:

> Thanks for your answer, the models represent two different tables,

> identical structure but have to be segregated, there is no better

> design options to implement them. Any leads on how to do the join?

 

Think about what the join needs to do. Find duplicates? Get all of them in either table?

Provide the right question and Django will do the right join.

--

Melvyn Sopacua

[Matthew Pava]

Why are there no better design options to implement them?  Are the tables being used in another software that you have no control over?

I would just merge the two tables and use one model.

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[aysh...@gmail.com]

Tables are coming from different sources, for each single datetime value there is a different url, in order to tie up the single source data it must live inside its own table.

On Wednesday, March 8, 2017 at 9:11:42 AM UTC-7, Matthew Pava wrote:

Why are there no better design options to implement them?  Are the tables being used in another software that you have no control over?

I would just merge the two tables and use one model.

 

From: django...@googlegroups.com [mailto:django...@googlegroups.com] On Behalf Of aysh...@gmail.com
Sent: Wednesday, March 8, 2017 8:24 AM
To: Django users
Subject: Re: Simple Join with no matching primary keys

 

 

Thanks for your answer, the models represent two different tables, identical structure but have to be segregated, there is no better design options to implement them. Any leads on how to do the join?

 

 

Models cannot be joined. There is no Model.join(). Models are objects you can relate to eachother.

Once you stop thinking in database terms, the problem is easily solved.

 

Since the two models are identical, why would you use two models? Your problem starts with your design - rethink it.

--

Melvyn Sopacua

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[Scot Hacker]

On Wednesday, March 8, 2017 at 8:39:43 AM UTC-8, aysh...@gmail.com wrote:

Tables are coming from different sources, for each single datetime value there is a different url, in order to tie up the single source data it must live inside its own table.

So why not make them into one table? You already have a field for `source` to distinguish the data source of each. Two tables with an identical set of fields is a code smell, IMO. 

./s

[Camilo Torres]

You can also create a database view from the join of the two tables.