如何在QuerySet中过滤空或NULL名称? [英] How to filter empty or NULL names in a QuerySet?

问题描述

我有 first_name ， last_name &我需要搜索的 alias (可选).因此，我需要查询以提供所有设置了别名的名称.

I have first_name, last_name & alias (optional) which I need to search for. So, I need a query to give me all the names that have an alias set.

只有我能做:

Name.objects.filter(alias!="")

那么，上述等同于什么?

So, what is the equivalent to the above?

推荐答案

您可以执行以下操作:

Name.objects.exclude(alias__isnull=True)

如果您需要排除空值和空字符串，则首选方法是将条件链接在一起，例如:

If you need to exclude null values and empty strings, the preferred way to do so is to chain together the conditions like so:

Name.objects.exclude(alias__isnull=True).exclude(alias__exact='')

将这些方法捆绑在一起基本上可以独立地检查每个条件:在上面的示例中，我们排除了 alias 为null 或为空字符串的行，因此得到所有 Name 对象具有非空，非空的 alias 字段.生成的SQL类似于:

Chaining these methods together basically checks each condition independently: in the above example, we exclude rows where alias is either null or an empty string, so you get all Name objects that have a not-null, not-empty alias field. The generated SQL would look something like:

SELECT * FROM Name WHERE alias IS NOT NULL AND alias != ""

您还可以将多个参数传递给对 exclude 的单个调用，这将确保仅将满足 every 条件的对象排除在外:

You can also pass multiple arguments to a single call to exclude, which would ensure that only objects that meet every condition get excluded:

Name.objects.exclude(some_field=True, other_field=True)

此处，其中 some_field 和 other_field 为真的行被排除，因此我们得到所有两个字段都不为真的行.生成的SQL代码看起来像这样:

Here, rows in which some_field and other_field are true get excluded, so we get all rows where both fields are not true. The generated SQL code would look a little like this:

SELECT * FROM Name WHERE NOT (some_field = TRUE AND other_field = TRUE)

或者，如果您的逻辑比这更复杂，则可以使用Django的 Q对象:

Alternatively, if your logic is more complex than that, you could use Django's Q objects:

from django.db.models import Q
Name.objects.exclude(Q(alias__isnull=True) | Q(alias__exact=''))

有关更多信息，请参见此页面和此页面.

For more info see this page and this page in the Django docs.

_{顺便说一句:我的SQL示例只是一个类比-实际生成的SQL代码可能看起来有所不同.通过实际查看它们生成的SQL，您将对Django查询的工作方式有更深入的了解.}

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