sqlalchemy and double outerjoin

Question

I need to do double outer join on following 2 tables A and B to get presented result using SQLAlchemy ORM or SQL expressions. Table B should be outer joined twice to get joined 2 result sets (distinguished by c_id) that are for the same A records. Outer join is used to get NULLs where B results are missing either in first (c_id = 66) or second (c_id = 70) outer join. A table: ``` id -- 1 2 3 4 ``` B table: ``` id | a_id | c_id ---+------+------ 1 | 1 | 66 2 | 2 | 66 3 | 3 | 70 4 | 4 | 66 5 | 4 | 70 ``` Query result should be: ``` a_id | b1_id (66) | b2_id (70) -----+------------+----------- 1 | 1 | NULL 2 | 2 | NULL 3 | NULL | 3 4 | 4 | 5 ``` I got to the point where proper raw SQL query looks as follows: ``` SELECT A.id AS a_id, B_1.id AS b1_id, B_2.id AS b2_id, FROM A LEFT OUTER JOIN B AS B_1 ON A.id = B_1.a_id AND B_1.c_id = 66 LEFT OUTER JOIN B AS B_2 ON A.id = B_2.a_id AND B_2.c_id = 70 WHERE B_1.id is not NULL or B_2.id is not NULL; ``` Now, do you know how to get this coded eit…

Accepted Answer

Found the solution myself:

```
b1 = aliased(B)
b2 = aliased(B)
q = session.query(A.id, b1.id.label("b1_id"), b1.id.label("b2_id"))
q = q.outerjoin(b1, sqlalchemy.and_(A.id == b1.a_id, b1.c_id == 66))
q = q.outerjoin(b2, sqlalchemy.and_(A.id == b2.a_id, b2.c_id == 70))
q = q.filter(sqlalchemy.or_(b1.id != None, b2.id != None))
```

sqlalchemy and double outerjoin

Solution

Problem