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，在链接的问题中，SQLAlchemy生成以下形式的SQL：

SELECT * FROM (SELECT column_a FROM table_a UNION SELECT column_b FROM table_b)

但我希望SQLAlchemy能够生成如下的SQL：

SELECT column_a FROM table_a UNION SELECT column_b FROM table_b

后者SQL更短，不使用子查询，并做同样的事情。 SQLAlchemy可以生成像后一个查询一样的联合吗？

Answer 1

根据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')

你可以在SQLAlchemy中执行没有子查询的UNION吗？

1 个答案: