在查询集中过滤空或NULL名称 [英] Filtering for empty or NULL names in a queryset

问题描述

我有first_name，last_name&我需要搜索的别名（可选）。所以，我需要一个查询来给我所有的名字设置别名。

只有我能做到：

  Name.objects.filter（alias！=）
  

那么等于上面的那个？

解决方案

你可以这么做：

  Name.objects.exclude（alias__isnull = True）
  

如果您需要排除空字符串和空字符串，首选的方法是将条件链接在一起：

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

将这些方法链接在一起基本上独立地检查每个条件：在上面的例子中，我们排除了别名的行是null 或一个空字符串，所以您得到所有​​名称对象具有非空，不为空的别名字段。生成的SQL将如下所示：

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

您还可以将多个参数传递给单个调用 exclude ，这将确保只有满足每个条件的对象被排除：

  Name.objects。排除（some_field = True，other_field = True）
  

这里， some_field 和 other_field 是真的被排除，所以我们得到两个字段不是真的所有行。生成的SQL代码看起来有点像这样：

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

或者，如果你的逻辑比这更复杂，你可以做这样的事情，虽然我只推荐它作为最后的手段：

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

有关详细信息，请参阅此页面和这个页面在Django文档中。

_{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。您将通过实际查看生成的SQL来更深入地了解Django查询的工作原理。}

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.

Only if I could do:

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

So, what is the equivalent to the above?

解决方案

You could do this:

Name.objects.exclude(alias__isnull=True)

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='')

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 != ""

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)

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)

Alternatively, if your logic is more complex than that, you could do something like this, although I only recommend it as a last resort:

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

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

_{As an aside: My SQL examples are just an analogy--the actual generated SQL code will probably look different. You'll get a deeper understanding of how Django queries work by actually looking at the SQL they generate.}

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