On Apr 11, 3:11 am, Malcolm Tredinnick <malc...@pointy-stick.com>
wrote:
> Django's SQL is going exactly what you suspect and not using any outer
> join here. Using a simplified version of the original two models:
>
> class Student(models.Model):
> ...
>
> class Message(models.Model):
> title = models.CharField(max_length=50)
> student = models.ForeignKey(Student)
>
> ... the SQL that is generated for Message.objects.filter(student=None)
> is:
>
> SELECT `outer_message`.`id`, `outer_message`.`title`,
> `outer_message`.`student_id` FROM `outer_message` WHERE
> `outer_message`.`student_id` IS NULL
Yes, this correctly if student = models.ForeignKey(Student).
I use this simplified models with student = models.ForeignKey
(Student, null=True), sql that is generated for Message.objects.filter
(student=None) is:
SELECT "messages_message"."id", "messages_message"."title",
"messages_message"."student_id" FROM "messages_message" LEFT OUTER
JOIN "messages_student" ON ("messages_message"."student_id" =
"messages_student"."id") WHERE "messages_student"."id" IS NULL
i use django svn-10510
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