How can I get computed elements of a table in a django queryset?

Question

I\'m trying to use django\'s queryset API to emulate the following query:

SELECT EXTRACT(year FROM chosen_date) AS year, 
EXTRACT(month FROM chosen_date) AS          


        

Answer 1

Would this work?:

from django.db import connection, transaction
cursor = connection.cursor()

sql = """
    SELECT 
        %s AS year, 
        %s AS month,
        date_paid IS NOT NULL as is_paid
    FROM (
        SELECT
            (CASE WHEN date_due IS NULL THEN date_due ELSE date END) AS chosen_date, *
        FROM
            invoice_invoice
    ) as t1;
    """ % (connection.ops.date_extract_sql('year', 'chosen_date'),
           connection.ops.date_extract_sql('month', 'chosen_date'))

# Data retrieval operation - no commit required
cursor.execute(sql)
rows = cursor.fetchall()

I think it's pretty save both CASE WHEN and IS NOT NULL are pretty db agnostic, at least I assume they are, since they are used in django test in raw format..