在django中使用条件注解时出错：选择\格式

pxy2qtax 于 2021-06-21 发布在 Mysql

关注(0)|答案(2)|浏览(405)

当试图注解查询集时，我从django方法得到一个typeerror。我在ubuntu上使用的是Django1.11.12和MySQL5.7.22。
这是我的模型.py：

class Group(models.Model):
    name = models.CharField(max_length=100)
class ActivationRecord(models.Model):
    group = models.ForeignKey('directory.Group')
    year = models.PositiveIntegerField()

如果一个团体在某一年有记录，它就是“活跃的”。我正在尝试使用以下查询注解组是否处于活动状态：

Group.objects.annotate(active=Case(
    When(activationrecord__year=2018, then=True), default=False, output_field=BooleanField))

当我运行时，会出现以下错误：

File "/home/vagrant/Envs/think/lib/python3.5/site-packages/django/db/models/query.py", line 226, in __repr__
    data = list(self[:REPR_OUTPUT_SIZE + 1])
  File "/home/vagrant/Envs/think/lib/python3.5/site-packages/django/db/models/query.py", line 250, in __iter__
    self._fetch_all()
  File "/home/vagrant/Envs/think/lib/python3.5/site-packages/django/db/models/query.py", line 1118, in _fetch_all
    self._result_cache = list(self._iterable_class(self))
  File "/home/vagrant/Envs/think/lib/python3.5/site-packages/django/db/models/query.py", line 53, in __iter__
    results = compiler.execute_sql(chunked_fetch=self.chunked_fetch)
  File "/home/vagrant/Envs/think/lib/python3.5/site-packages/django/db/models/sql/compiler.py", line 877, in execute_sql
    sql, params = self.as_sql()
  File "/home/vagrant/Envs/think/lib/python3.5/site-packages/django/db/models/sql/compiler.py", line 429, in as_sql
    extra_select, order_by, group_by = self.pre_sql_setup()
  File "/home/vagrant/Envs/think/lib/python3.5/site-packages/django/db/models/sql/compiler.py", line 46, in pre_sql_setup
    self.setup_query()
  File "/home/vagrant/Envs/think/lib/python3.5/site-packages/django/db/models/sql/compiler.py", line 37, in setup_query
    self.select, self.klass_info, self.annotation_col_map = self.get_select()
  File "/home/vagrant/Envs/think/lib/python3.5/site-packages/django/db/models/sql/compiler.py", line 227, in get_select
    sql, params = self.compile(col, select_format=True)
  File "/home/vagrant/Envs/think/lib/python3.5/site-packages/django/db/models/sql/compiler.py", line 375, in compile
    return node.output_field.select_format(self, sql, params)
TypeError: select_format() missing 1 required positional argument: 'params'

mysql django

来源：https://stackoverflow.com/questions/50787881/error-when-using-conditional-annotation-in-django-select-format

2条答案

按热度按时间

nsc4cvqm1#

@莱梅泽尔的回答确实解决了这个问题。
另一种方法是使用 Exists 子查询：

from django.db.models import Exists, OuterRef
Group.objects.annotate(
    active=Exists(
        ActivationRecord.objects.filter(year=2018, group=OuterRef('pk'))
    )
)

这基本上Map到sql查询：

SELECT `group`.*, EXISTS(
    SELECT U0.*
    FROM `activationrecord` U0
    WHERE (U0.`group` = (`group`.pk)
           AND U0.`year` = 2018)
    ) AS `active`
FROM `group`

展开查看全部

赞(0）回复(0）举报 2021-06-21

deyfvvtc2#

BooleanField 需要作为函数调用，使用 () ```
Group.objects.annotate(active=Case(
When(activationrecord__year=2018, then=True),
default=False, output_field=BooleanField()))

赞(0）回复(0）举报 2021-06-21

我来回答

在django中使用条件注解时出错：选择\格式

2条答案

相关问题

热门标签

最新问答