`sum`、`average`、`min`、`max`的sqlalchemy简单示例

Question

For sqlalchemy , Who can gently give simple examples of SQL functions like sum , average , min , max , for a column ( score in the following as an example).

As for this mapper:

class Score(Base):
    #...
    name = Column(String)
    score= Column(Integer)
    #...

Answer 1

See SQL Expression Language Tutorial for the usage. The code below shows the usage:

from sqlalchemy.sql import func
qry = session.query(func.max(Score.score).label("max_score"), 
                    func.sum(Score.score).label("total_score"),
                    )
qry = qry.group_by(Score.name)
for _res in qry.all():
    print _res

Answer 2

From SQLAlchemy docs , for sum method, we need to use functions.sum() . As we can see:

from sqlalchemy.sql import functions

result = session.query(
    functions.sum(Model.value_a + Model.value_b)
).scalar()

that will produce a sql like:

SELECT sum(public.model.value_a + public.model.value_b) AS sum_1 ...