Hierarchy Model

[Setiaman Lee]

Hi,

I want to implement hierarchy data model which is quite common in Relational Data Model.

Let's say I have Employee model which has the relation to the boss which link to the employee model itself.
It will look like this:

class Employee(models.Model):
    empname = models.CharField(max_length=60)
    boss = models.ForeignKey(Employee)
    salary = models.integer()


Sample Data:

ID    empname      boss        salary
--------------------------------------------------
1      albert            null          10000
2      bert              1              5000
3      Chuck          1              5000
4      Donna          3              3000
5      Jack            3              2000
 
Albert is the root with Bert and Chuck under him and Chuck has Donna and Jack under him.

I got an error when I tried to sync to the database where Django telling me that the employee is not exist in the Foreign key part.
Is there any way to manipulate this situation?

Cheers,
Setiaman

[Andre Terra]

-- Sent from my phone, please excuse any typos. --

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[Andre Terra]

I recommend using django-mptt. I can't link to it cause I'm writing on my phone, but it's easy to find it on Google.

Also, your foreign key should target self rather than Employee, IIRC.

Cheers,
AT

-- Sent from my phone, please excuse any typos. --

On Jul 15, 2012 11:02 AM, "Setiaman Lee" <setiam...@gmail.com> wrote:

--

[lacry...@gmail.com]

Put 'Employee' or if that fails, 'appname.Employee' with the quotes, as a string literal, this works for self-reference and reference loops.

-----Mensaje original-----
De: Andre Terra
Enviados: 15/07/2012 13:30:05
Asunto: Re: Hierarchy Model

[yarko]

On Sunday, July 15, 2012 9:02:39 AM UTC-5, Setiaman wrote:

Hi,

I want to implement hierarchy data model which is quite common in Relational Data Model.

Let's say I have Employee model which has the relation to the boss which link to the employee model itself.
It will look like this:

class Employee(models.Model):
    empname = models.CharField(max_length=60)
    boss = models.ForeignKey(Employee)

Employee is in the middle of being defined when you make this reference, so
... try something like:

    boss = models.ForeignKey('Employee')   # delayed evaluation

or:

   boss = models.ForeignKey('self')  # I think this reads nicer

See https://docs.djangoproject.com/en/dev/ref/models/fields/#foreignkey

    salary = models.integer()


Sample Data:

ID    empname      boss        salary
--------------------------------------------------
1      albert            null          10000
2      bert              1              5000
3      Chuck          1              5000
4      Donna          3              3000
5      Jack            3              2000
 
Albert is the root with Bert and Chuck under him and Chuck has Donna and Jack under him.

I got an error when I tried to sync to the database where Django telling me that the employee is not exist in the Foreign key part.
Is there any way to manipulate this situation?

Cheers,
Setiaman

Regards,
Yarko

[Setiaman Lee]

Hi All,

It works by blocking it with the single quote. :)
Thanks for the help.

Cheers,
Setiaman

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