python - How to perform a left join in SQLALchemy?

Question

I have a SQL query which perfroms a series of left joins on a few tables:

SELECT
<some attributes>
FROM table1 t1
INNER JOIN table2 t2
      ON attr = 1 AND attr2 = 1
LEFT JOIN table3 t3
    ON t1.Code = t2.Code AND t3.Date_ = t1.Date_
LEFT JOIN tabl4 t4
    ON t4.Code = t1.code AND t4.Date_ = t1.Date_

So far, I have:

(sa.select([idc.c.Code])
            .select_from(
                t1.join(t2, and_(t1.c.attr == 1, t2.c.attr2 = 1))
                .join(t3, t3.c.Code == t1.c.Code)))

but I can't figure out how to make the join a LEFT JOIN.

Answer 1

The isouter=True flag will produce a LEFT OUTER JOIN which is the same as a LEFT JOIN.

With your code:

(sa.select([idc.c.Code])
        .select_from(
            t1.join(t2, and_(t1.c.attr == 1, t2.c.attr2 = 1))
            .join(t3, t3.c.Code == t1.c.Code, isouter=True)))

Declarative example:

session = scoped_session(sessionmaker())
session.query(Model).join(AnotherModel, AnotherModel.model_id == Model.id, isouter=True)