Flask SQLAlchemy filter by value OR another

问题

I have a Flask project that interacts with MySQL db through Flask-SQLAlchemy.

My question is, how to select a row from the database based on a value OR another value.

The results I want in SQL looks like this

SELECT id FROM users WHERE email=email OR name=name;

How to achieve that in Flask-SQLAlchemy?

回答1:

The following may help:

# app.py
from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'url_or_path/to/database'
db = SQLAlchemy(app)

class User(db.Model):
    __tablename__ = 'users'
    id = db.Column(db.Integer, primary_key=True)
    email = db.Column(db.String(50), unique=True)
    name = db.Column(db.String(30))

    def __init__(self, name=None, email=None):
        if not name:
            raise ValueError('\'name\' cannot be None')
        if not email:
            raise ValueError('\'email\' cannot be None')
        self.name = name
        self.email = email

class UserQuery(object):
    @staticmethod
    def get_user_id_by_email_or_name(email=None, name=None):
        user = User.query.filter((User.email == email) | (User.name == name)).first()
        return user.id if hasattr(user, 'id') else None

The '|' can be used inside a filter instead of 'or_'. See Using OR in SQLAlchemy.

You can use like this:

>>> from app import db, User, UserQuery
>>> db.create_all()
>>> user = User(name='stan', email='stan@email.com')
>>> db.session.add(user)
>>> db.session.commit()
>>> by_name_id = UserQuery.get_user_id_by_email_or_name(name='stan')
>>> by_email_id = UserQuery.get_user_id_by_email_or_name(email='stan@email.com')
>>> by_name_id == by_email_id
True

回答2:

I also needed this case today, I found the nice answer here:

So, we can make OR logic like the below example:

from sqlalchemy import or_
db.session.query(User).filter(or_(User.email=='useremail@example.com', User.name=="username")).first()

When using the filter() expression, you must use proper comparison operators, whereas filter_by() uses a shortened unPythonic form.

回答3:

I also wanted to have an or along with and condition

I found this after googling around:

# Users whose age is 23 AND (firstname IS alex OR lastname IS watson)
usrs = session.query(User) \
    .filter(User.age === "23") \
    .filter((User.firstname == 'alex') | (User.lastname == 'watson')) \
    .all()

hopefully, it helps other people coming here looking for it

来源：https://stackoverflow.com/questions/40535547/flask-sqlalchemy-filter-by-value-or-another

标签

python

mysql

flask-sqlalchemy