[Django]-Raw SQL query in Django

You can delete your record(s) directly via connection.cursor() (docs):

from django.db import connection

cursor = connection.cursor()
cursor.execute('DELETE FROM costumer_worker WHERE costumer_ptr_id = %s', [costumer.id])
connection.commit()

But, the thing you’re trying to do looks too simple to write SQL directly, use django ORM instead.

You may be missing comitting the transcation. Based on your settings, you may need to add :
transaction.commit_unless_managed() in django 1.4 ( not needed in django 1.5, since default settings are different)

use this line:

from django.db import connection, transaction
cursor = connection.cursor()
with transaction.commit_on_success():
   cursor.execute('DELETE FROM costumer_worker WHERE costumer_ptr_id = %s', [costumer.id])
   connection.commit()