Obvious Django tip: one query is better than two

To often, I see unnecessary queries in Django code: first get a complete data object, just so it can be used in another query.

For example, we have an employee_id and want to get the Company of the Employee (both data models, where employee is the ForeignKey field of Company).

So, don't do this:
# get Employee object
try:
    employee = Employee.objects.get(id = employee_id)
except ObjectDoesNotExist:
    pass
# get Company object
try:
    company = Company.objects.get(employee = employee)
except ObjectDoesNotExist:
    pass

But instead, make a single query, directly using the ForeignKey:
# get Company object
try:
    company = Company.objects.get(employee__id = employee_id)
except ObjectDoesNotExist:
    pass

See https://docs.djangoproject.com/en/dev/topics/db/queries/ for more info

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