如何过滤 QuerySet 中的空名称或 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).所以，我需要一个查询来给我所有设置了别名的名字.

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.

如果我能做到:

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

那么，上面的等价物是什么?

So, what is the equivalent to the above?

推荐答案

你可以这样做:

Name.objects.exclude(alias__isnull=True)

如果您需要排除空值和空字符串，最好的方法是将条件链接在一起，如下所示:

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='')

将这些方法链接在一起基本上独立检查每个条件:在上面的示例中，我们排除了 alias 为 null 或 为空字符串的行，因此您将获得所有 Name 具有非空、非空 alias 字段的对象.生成的 SQL 看起来像:

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，这将确保只有满足所有条件的对象才会被排除:

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)

这里，some_field 和 other_field 为真的行被排除，因此我们得到两个字段都不为真的所有行.生成的 SQL 代码看起来有点像这样:

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，您可以使用 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，请参阅此页面和此页面 在 Django 文档中.

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 代码可能看起来不同.通过实际查看它们生成的 SQL，您将更深入地了解 Django 查询的工作原理.}

这篇关于如何过滤 QuerySet 中的空名称或 NULL 名称?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！