sqlalchemy - 你能在 SQLAlchemy 中没有子查询的情况下执行 UNION 吗？

Question

Another question shows how to do a union in SQLAlchemy.

是否可以在不使用子查询的情况下在 SQLAlchemy 中执行联合？

例如，在链接问题 SQLAlchemy 中生成的 SQL 形式如下:
SELECT * FROM (SELECT column_a FROM table_a UNION SELECT column_b FROM table_b)
但我希望 SQLAlchemy 生成如下 SQL:
SELECT column_a FROM table_a UNION SELECT column_b FROM table_b
后一个 SQL 更短，不使用子查询，并且做同样的事情。 SQLAlchemy 可以生成像后一个查询那样的联合吗？

Answer 1

每 SQLAlchemy SQL Expression Language Tutorial :

您可以使用 sqlalchemy.sql.expression.union :

>>> from sqlalchemy.sql import union
>>> u = union(
...     addresses.select().
...             where(addresses.c.email_address == 'foo@bar.com'),
...    addresses.select().
...             where(addresses.c.email_address.like('%@yahoo.com')),
... ).order_by(addresses.c.email_address)

>>> u.compile()
SELECT addresses.id, addresses.user_id, addresses.email_address FROM
addresses WHERE addresses.email_address = ?
UNION
SELECT addresses.id,
addresses.user_id, addresses.email_address FROM addresses WHERE
addresses.email_address LIKE ? ORDER BY addresses.email_address
('foo@bar.com', '%@yahoo.com')