python - How to execute "left outer join" in SqlAlchemy

Question

I need to execute this query::

select field11, field12
from Table_1 t1
left outer join Table_2 t2 ON t2.tbl1_id = t1.tbl1_id
where t2.tbl2_id is null

I had these classes in python:

class Table1(Base):
   ....

class Table2(Base):
   table_id =  Column(
        Integer,
        ForeignKey('Table1.id', ondelete='CASCADE'),
    )
    ....

How do I get to the above from the below?

Answer 1

q = session.query(Table1.field1, Table1.field2)
    .outerjoin(Table2) # use in case you have relationship defined
    # .outerjoin(Table2, Table1.id == Table2.table_id) # use if you do not have relationship defined
    .filter(Table2.tbl2_id == None)

should do it, assuming that field1 and field2 are from Table1, and that you define a relationship:

class Table2(Base):
    # ...
    table1 = relationship(Table1, backref="table2s")