SQLAlchemy ORDER BY DESCENDING?

问题:

How can I use ORDER BY descending in a SQLAlchemy query like the following?

This query works, but returns them in ascending order:

query = (model.Session.query(model.Entry)
        .join(model.ClassificationItem)
        .join(model.EnumerationValue)
        .filter_by(id=c.row.id)
        .order_by(model.Entry.amount) # This row :)
        )

If I try:

.order_by(desc(model.Entry.amount))

then I get: NameError: global name 'desc' is not defined.

回答1:

Just as an FYI, you can also specify those things as column attributes. For instance, I might have done:

.order_by(model.Entry.amount.desc())

This is handy since you can use it on other places such as in a relation definition, etc.

For more information, you can refer this

回答2:

from sqlalchemy import desc
someselect.order_by(desc(table1.mycol))

Usage from @jpmc26

回答3:

One other thing you might do is:

.order_by("name desc")

This will result in: ORDER BY name desc. The disadvantage here is the explicit column name used in order by.

回答4:

You can use .desc() function in your query just like this

query = (model.Session.query(model.Entry)
        .join(model.ClassificationItem)
        .join(model.EnumerationValue)
        .filter_by(id=c.row.id)
        .order_by(model.Entry.amount.desc())
        )

This will order by amount in descending order or

query = session.query(
    model.Entry
).join(
    model.ClassificationItem
).join(
    model.EnumerationValue
).filter_by(
    id=c.row.id
).order_by(
    model.Entry.amount.desc()
)
)

回答5:

Complementary at @Radu answer, As in SQL, you can add the table name in the parameter if you have many table with the same attribute.

.order_by("TableName.name desc")

回答6:

We can do it in multiple ways.The simplest one will be to do it in the following way-

res=ModelName.query.filter(ModelName.var1==cond).order_by(ModelName.var1.desc())