左加入Django ORM
左加入Django ORM
提问于 2014-01-22 00:21:07
我有以下几种型号：
class Volunteer(models.Model):
first_name = models.CharField(max_length=50L)
last_name = models.CharField(max_length=50L)
email = models.CharField(max_length=50L)
gender = models.CharField(max_length=1, choices=GENDER_CHOICES)
class Department(models.Model):
name = models.CharField(max_length=50L, unique=True)
overseer = models.ForeignKey(Volunteer, blank=True, null=True)
location = models.CharField(max_length=100L, null=True)
class DepartmentVolunteer(models.Model):
volunteer = models.ForeignKey(Volunteer)
department = models.ForeignKey(Department)
assistant = models.BooleanField(default=False)
keyman = models.BooleanField(default=False)
captain = models.BooleanField(default=False)
location = models.CharField(max_length=100L, blank=True, null=True)我想查询所有没有志愿者的部门。我可以使用以下查询来做到这一点：
SELECT
d.name
FROM
vsp_department AS d
LEFT JOIN vsp_departmentvolunteer AS dv
ON d.id = dv.department_id
WHERE
dv.department_id IS NULL;是否有一种更像django的方法来这样做，或者我应该只使用原始sql？
Stack Overflow用户
发布于 2017-06-27 08:40:51
通过或创建自定义连接
def get_queryset(self):
qs = super(AceViewSet, self).get_queryset()
qs = qs.select_related('xxx')
# construct all tables and the join dependence
qs.query.__str__()
qs.query.alias_map['xx_subject'].join_cols = (('xxx_id', 'uid'), ('xxx_id', 'ad_subject_id'))
qs.query.alias_map['xx_subject'].as_sql = partial(self.as_sql, qs.query.alias_map['xx_subject'])
return qs
@staticmethod
def as_sql(self, compiler, connection):
sql, params = Join.as_sql(self, compiler, connection)
or_sql = sql.replace("AND", "OR")
return or_sql, paramsFROM "xx_ace"
LEFT OUTER JOIN "xx_subject"
ON ("xx_ace"."xxx_id" = "xx_subject"."uid" OR "xx_ace"."xxx_id" = "xx_subject"."ad_subject_id")页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/21271835
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