I have two tables beard and moustache defined below:
+--------+---------+------------+-------------+ | person | beardID | beardStyle | beardLength | +--------+---------+------------+-------------+ +--------+-------------+----------------+ | person | moustacheID | moustacheStyle | +--------+-------------+----------------+
I have created a SQL Query in PostgreSQL which will combine these two tables and generate following result:
+--------+---------+------------+-------------+-------------+----------------+ | person | beardID | beardStyle | beardLength | moustacheID | moustacheStyle | +--------+---------+------------+-------------+-------------+----------------+ | bob | 1 | rasputin | 1 | | | +--------+---------+------------+-------------+-------------+----------------+ | bob | 2 | samson | 12 | | | +--------+---------+------------+-------------+-------------+----------------+ | bob | | | | 1 | fu manchu | +--------+---------+------------+-------------+-------------+----------------+
Query:
SELECT * FROM beards LEFT OUTER JOIN mustaches ON (false) WHERE person = "bob" UNION ALL SELECT * FROM beards b RIGHT OUTER JOIN mustaches ON (false) WHERE person = "bob"
However I can not create SQLAlchemy representation of it. I tried several ways from implementing from_statement to outerjoin but none of them really worked. Can anyone help me with it?
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Answer
From @Francis P‘s suggestion I came up with this snippet:
q1 = session.
     query(beard.person.label('person'),
           beard.beardID.label('beardID'),
           beard.beardStyle.label('beardStyle'),
           sqlalchemy.sql.null().label('moustachID'),
           sqlalchemy.sql.null().label('moustachStyle'),
     ).
     filter(beard.person == 'bob')
q2 = session.
     query(moustache.person.label('person'),
           sqlalchemy.sql.null().label('beardID'), 
           sqlalchemy.sql.null().label('beardStyle'),
           moustache.moustachID,
           moustache.moustachStyle,
     ).
     filter(moustache.person == 'bob')
result = q1.union(q2).all()
However this works but you can’t call it as an answer because it appears as a hack. This is one more reason why there should be RIGHT OUTER JOIN in sqlalchemy.