Python如何使用sqlalchemy实现动态sql

from sqlalchemy import create_engine, Column, Integer, String
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

# 创建数据库引擎
engine = create_engine('sqlite:///example.db')

# 创建会话
Session = sessionmaker(bind=engine)
session = Session()

# 定义模型
Base = declarative_base()

class User(Base):
    __tablename__ = 'users'
    id = Column(Integer, primary_key=True)
    name = Column(String)
    age = Column(Integer)

# 动态构建查询
def get_users(filters):
    query = session.query(User)
    
    if 'name' in filters:
        query = query.filter(User.name == filters['name'])
    
    if 'age' in filters:
        query = query.filter(User.age == filters['age'])
    
    return query.all()

# 示例调用
filters = {'name': 'Alice', 'age': 30}
users = get_users(filters)
for user in users:
    print(user.name, user.age)

from sqlalchemy import and_, or_

def get_users(filters):
    query = session.query(User)
    
    conditions = []
    if 'name' in filters:
        conditions.append(User.name == filters['name'])
    
    if 'age' in filters:
        conditions.append(User.age == filters['age'])
    
    if conditions:
        query = query.filter(and_(*conditions))
    
    return query.all()

# 示例调用
filters = {'name': 'Alice', 'age': 30}
users = get_users(filters)
for user in users:
    print(user.name, user.age)

from sqlalchemy import text

def get_users(filters):
    query = "SELECT * FROM users WHERE 1=1"
    
    params = {}
    if 'name' in filters:
        query += " AND name = :name"
        params['name'] = filters['name']
    
    if 'age' in filters:
        query += " AND age = :age"
        params['age'] = filters['age']
    
    result = session.execute(text(query), params)
    return result.fetchall()

# 示例调用
filters = {'name': 'Alice', 'age': 30}
users = get_users(filters)
for user in users:
    print(user.name, user.age)

from sqlalchemy import lambda_
from sqlalchemy.orm import aliased

def get_users(filters):
    query = session.query(User)
    
    if 'name' in filters:
        query = query.filter(lambda: User.name == filters['name'])
    
    if 'age' in filters:
        query = query.filter(lambda: User.age == filters['age'])
    
    return query.all()

# 示例调用
filters = {'name': 'Alice', 'age': 30}
users = get_users(filters)
for user in users:
    print(user.name, user.age)