问题：sqlalchemy不为空选择

如何像在SQL中一样添加过滤器，以从特定列中选择非空值？

SELECT * 
FROM table 
WHERE YourColumn IS NOT NULL;

如何使用SQLAlchemy过滤器执行相同操作？

select = select(table).select_from(table).where(all_filters)
点击查看英文原文

How can I add the filter as in SQL to select values that are NOT NULL from a certain column ?

SELECT * 
FROM table 
WHERE YourColumn IS NOT NULL;

How can I do the same with SQLAlchemy filters?

select = select(table).select_from(table).where(all_filters)

回答 0

column_obj != None会产生一个IS NOT NULL约束：

在列上下文中，产生子句a != b。如果目标是None，则生成一个IS NOT NULL。

或使用isnot()（0.7.9中的新功能）：

实施IS NOT操作员。

通常，IS NOT当与的值进行比较时，会自动生成None，解析为NULL。但是，IS NOT如果与某些平台上的布尔值进行比较，则可能需要显式使用。

演示：

>>> from sqlalchemy.sql import column
>>> column('YourColumn') != None
<sqlalchemy.sql.elements.BinaryExpression object at 0x10c8d8b90>
>>> str(column('YourColumn') != None)
'"YourColumn" IS NOT NULL'
>>> column('YourColumn').isnot(None)
<sqlalchemy.sql.elements.BinaryExpression object at 0x104603850>
>>> str(column('YourColumn').isnot(None))
'"YourColumn" IS NOT NULL'
点击查看英文原文

column_obj != None will produce a IS NOT NULL constraint:

In a column context, produces the clause a != b. If the target is None, produces a IS NOT NULL.

or use isnot() (new in 0.7.9):

Implement the IS NOT operator.

Normally, IS NOT is generated automatically when comparing to a value of None, which resolves to NULL. However, explicit usage of IS NOT may be desirable if comparing to boolean values on certain platforms.

Demo:

>>> from sqlalchemy.sql import column
>>> column('YourColumn') != None
<sqlalchemy.sql.elements.BinaryExpression object at 0x10c8d8b90>
>>> str(column('YourColumn') != None)
'"YourColumn" IS NOT NULL'
>>> column('YourColumn').isnot(None)
<sqlalchemy.sql.elements.BinaryExpression object at 0x104603850>
>>> str(column('YourColumn').isnot(None))
'"YourColumn" IS NOT NULL'

回答 1

从0.7.9版本开始，您可以使用filter运算符.isnot而不是比较约束，如下所示：

query.filter(User.name.isnot(None))

仅当担心pep8时才需要此方法。

来源：sqlalchemy文档

点击查看英文原文

Starting in version 0.7.9 you can use the filter operator .isnot instead of comparing constraints, like this:

query.filter(User.name.isnot(None))

This method is only necessary if pep8 is a concern.

source: sqlalchemy documentation

回答 2

如果其他人想知道，可以使用is_生成foo IS NULL：

>>>来自sqlalchemy.sql导入列
>>>打印列（'foo'）。is_（无）
foo IS NULL
>>>打印列（'foo'）。isnot（无）
foo不为空
点击查看英文原文

In case anyone else is wondering, you can use is_ to generate foo IS NULL:

>>> from sqlalchemy.sql import column
>>> print column('foo').is_(None)
foo IS NULL
>>> print column('foo').isnot(None)
foo IS NOT NULL
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