New user - struggling with database design

[Jason G]

Hi all,

I am building an app to track my home brewing.

I have two tables, one for vessels, and another for brews.

I want the Brew table to have a pick-list, relation to Vessels so I can say what vessel the brew is in.

I also want to render a table that shows all Vessels and what Brew is in each. There should be a one-to-one relationship until the Brew is 'Kicked', which could be a vessel or maybe a null value in the Brew table.

My code currently doesn't work, but looks something like this:

class Vessel(models.Model):

    Name = models.CharField(max_length=20)

    Gallons = models.DecimalField(max_digits=4, decimal_places=2, null=True, blank=True)

    Weight = models.DecimalField(max_digits=4, decimal_places=2, null=True, blank=True)

    CurrentBrew  = models.ForeignKey(Brew, db_column='Vessel')  <--------------------------------------this is what I'm trying to add

    def __unicode__(self):

        return self.Name

class Brew(models.Model):

    ...

    Name = models.CharField(max_length=40, null=True, default='TBD')

    InformalName = models.CharField(max_length=40)

    Status = models.IntegerField(max_length=1, choices=STATUS_CHOICES, default=1, null=False, blank=False)

    Gallons = models.DecimalField(max_digits=4, decimal_places=2, null=True, blank=True)

    Vessel = models.ForeignKey(Vessel)

    Style = models.ForeignKey(Style)

    Event = models.CharField(max_length=40, null=True, blank=True)

In this model, which I'm not sure is the best way to do it, the Vessel class does not yet know about the Brew model that is below it.

I'm starting to grasp this language (and love it, coming from doing asp/sql several years ago) but I'm stuck here. Help!

[Gerald Klein]

their order if I am understanding you right does not effect this, the last part is just  a join between the tables, you don't have to create another table

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[Jason G]

Hi Gerald - thanks for the quick reply! Turns out it was just an issue with quotes...not sure I am doing it right just yet, but at least I've passed the error.

[Jason G]

Ok - here is where I am stuck now. Any thoughts?

If I try to render {{ vessel.CurrentBrew }} in a view, I get something like this:

<django.db.models.fields.related.ManyRelatedManager object at 0x7f76f0088e10>

and this errors out:

{% for Brew in vessel.CurrentBrew.all %}X{{ Brew.ActualName }}<br/>{% endfor %}

(1146, "Table 'dbLunawireBrewing.brewlog_vessel_CurrentBrew' doesn't exist")

The vessel model looks like this:

class Vessel(models.Model):
    Name = models.CharField(max_length=20)
    ShortName = models.CharField(max_length=4)
    Gallons = models.DecimalField(max_digits=4, decimal_places=2, null=True, blank=True)
    Weight = models.DecimalField(max_digits=4, decimal_places=2, null=True, blank=True)
    CurrentBrew  = models.ManyToManyField('Brew', related_name="brew")
    def __unicode__(self):
        return self.Name

[Derek]

That looks like a database error - check in your database as to which tables have been created.