SQLAlchemy 应用过滤器基础教程文档
收录于 2023-04-20 00:10:05 · بالعربية · English · Español · हिंदीName · 日本語 · Русский язык · 中文繁體
在本章中,我们将讨论如何应用过滤器以及某些过滤器操作及其代码。
Query 对象表示的结果集可以通过使用 filter() 方法服从某些条件。 filter方法的一般用法如下-
session.query(class).filter(criteria)
在下面的例子中,通过对Customers表的SELECT查询得到的结果集被一个条件过滤,(ID>2)-
result = session.query(Customers).filter(Customers.id>2)
此语句将转换为以下 SQL 表达式-
SELECT customers.id AS customers_id, customers.name AS customers_name, customers.address AS customers_address, customers.email AS customers_email FROM customers WHERE customers.id > ?
由于绑定参数 (?) 为 2,因此只会显示 ID column>2 的行。完整代码如下-
from sqlalchemy import Column, Integer, String from sqlalchemy import create_engine engine = create_engine('sqlite:///sales.db', echo = true) from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() class Customers(Base): __tablename__ = 'customers' id = Column(Integer, primary_key = true) name = Column(String) address = Column(String) email = Column(String) from sqlalchemy.orm import sessionmaker Session = sessionmaker(bind = engine) session = Session() result = session.query(Customers).filter(Customers.id>2) for row in result: print ("ID:", row.id, "Name: ",row.name, "Address:",row.address, "Email:",row.email)
Python 控制台中显示的输出如下-
ID: 3 Name: Rajender Nath Address: Sector 40, Gurgaon Email: nath@gmail.com ID: 4 Name: S.M.Krishna Address: Budhwar Peth, Pune Email: smk@gmail.com