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"""mapper & fields/nested select
this is an example of a mapper with a nested select.
You can still use filters and constraints
"""
from sqlalchemy.orm import mapper, column_property
from sqlalchemy.sql import select, func
class Director2(object): pass
m = mapper(Director2, model.Director.__table__,
properties={
'film_number': column_property(
select(
[func.count(model.Movie.__table__.c.id)],
model.Director.__table__.c.id == model.Movie.__table__.c.director_id
).label('film_number')
)
}
)
field_list = "last_name, first_name, nation, film_number"
t = SqlTable(m, field_list=field_list, dbproxy=db)
t.add_filter(film_number=3)
t.add_constraint(film_number__lt = 5)
t.reload()
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