Use Raw Sql In An Orm Query

Is it possible to make edits or override the ORM's generated SQL with your own raw SQL? Or is the ORM expected to be flexible enough to build pretty much any query I could imagine?

Solution 1:

The answer by @Abdou is the proper way to go, but you could also run your textual SQL using Query.from_statement():

session.query(AllocationStatus).\
    from_statement(text("""
        SELECT allocation_status.*
        FROM allocation_status
        LEFT JOIN allocation_status allocation_status2
               ON allocation_status.allocation_id = allocation_status2.allocation_id
              AND allocation_status.id < allocation_status2.id
        WHERE allocation_status2.id IS NULL;""")).\
    all()

Note the use of text().

Solution 2:

You can build it by aliasing the Model first and then using that alias as the second table to an outer join. The following assumes that you already have a session that is bound to a working engine:

from sqlalchemy.orm import aliased
from sqlalchemy import and_


allocation_status2 = aliased(AllocationStatus)
session.query(AllocationStatus).\
    outerjoin(allocation_status2,
              and_(AllocationStatus.allocation_id == allocation_status2.allocation_id,
                   AllocationStatus.id < allocation_status2.id)).\
    filter(allocation_status2.id.is_(None)).all()

I hope this helps.