Django Union Query

Question

I need to develop a UNION query in Django with 3 models namely WebQuery,WebReply and BusinessOwners and the output should be of the form below.

{
    "(#conversation_id#)_(#b_id#)": {
        "from": "(#user_id)",
        "email": "(#user_email)",
        "date_time": "#get from db",
        "query": "are you open ?",
        "from_r_id": "(#representative_id)",
        "from_r_name": "(#rep_name)",
        "business_registered": "FALSE"
        "to_business_name": "CCD saket",
        "chat": [{
            "direction": 1,
            "text": "yes sir",
            "date_time": "424 577"
        }, {
            "direction": 0,
            "text": "ok",
            "date_time": "424 577"
        }]
    },

I know how to query when only one model is involved, but not sure of the union query. How will this be achieved?

can you show us the backend code you are looking to do the union on? And show us the code you have tried so far — karthikr, Jul 15 '13 at 14:01
@karthikr - Here is the link to my models.py file. Kindly review and provide the necessary help. Thanks :) [http://stackoverflow.com/questions/17651815/database-error-no-such-table-django/17653647?noredirect=1#17653647] — Praful Bagai, Jul 15 '13 at 15:47

score 0 · Answer 1 · edited May 23 '17 at 10:25

I personally would say that if this is going to be a common query then I would recommend making a SQL View then querying that.

w3schools has a VERY simple overview of what a view is : http://www.w3schools.com/sql/sql_view.asp

In SQL, a view is a virtual table based on the result-set of an SQL statement.

This means you can write your required sql statement and create a view using this. Then create a django model which mirrors that view which you can then use to query.

So, you will create an SQL view:

CREATE VIEW view_name AS
    SELECT a, b, c
    FROM table_name
    WHERE condition

Then create a django model, which has a slight difference to a normal model:

class view_name(models.Model):
    class Meta:
        # https://docs.djangoproject.com/en/1.5/ref/models/options/#django.db.models.Options.managed
        managed = False

    a = models.CharField(max_length)
    ....

managed = false > https://docs.djangoproject.com/en/1.5/ref/models/options/#django.db.models.Options.managed

You can then query this using the normal django orm syntax

Or there is similar questions:

Previous stackoverflow question, union in django orm

How can I find the union of two Django querysets?

I dont get it.Can you please be a more specific. Thanks. – Praful Bagai Jul 16 '13 at 01:32 — Praful Bagai, Jul 16 '13 at 01:32
@user1162512 see expanded answer – Matt Seymour Jul 16 '13 at 08:11 — Matt Seymour, Jul 16 '13 at 08:11

score 0 · Answer 2 · answered Jul 13 '17 at 22:42

0

How can I find the union of two Django querysets? provides an example of a union using the '|' operator. I'm not sure how different your models are. If there's common fields you could place those in a separate model and use model inheritance

answered Jul 13 '17 at 22:42

jocassid

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Django Union Query

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