python中使用SQLAlchemy（二）
阿新 • • 發佈：2019-02-18
由於目前工作比較忙，就借鑑其他大神的學習筆記，即使沒有聽課，但是也是看得懂下面的內容
關於SQLAlchemy使用建表、插入和查詢內容，點選python中使用SQLAlchemy檢視。
繼續以前面建立的student表作為示例進行後面的操作。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | mysql> desc student; +---------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | |
更新
更新時，首先查詢需要更新的資料，然後直接更新對應欄位即可。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 | from sqlalchemy import create_engine, Column, Integer, String from sqlalchemy.ext.declarative import declarative_base from sqlalchemy.orm import sessionmaker engine = create_engine("mysql+pymysql://root:[email protected]/test") DBsession = sessionmaker(bind=engine) session = DBsession() Base = declarative_base() class Student(Base): __tablename__ = 'student' id = Column(Integer, primary_key=True) name = Column(String(100)) age = Column(Integer) address = Column(String(100)) student1 = session.query(Student).filter(Student.name == 'Alice').one() print("更新前age：{0}".format(student1.age)) student1.age = '38' session.commit() print("更新後age：{0}".format(student1.age)) session.close() |
輸出結果
1 2 | 更新前age：25 更新後age：38 |
刪除
刪除時，首先查詢出需要刪除的資料，然後直接呼叫delete()方法直接刪除即可。
1 2 3 | student2 = session.query(Student).filter(Student.name == 'Alice').delete() session.commit() session.close() |
資料庫結果確認
1 2 3 4 5 6 7 8 | mysql> select * from student; +------+-------+------+---------+ | id | name | age | address | +------+-------+------+---------+ | 1002 | Bob | 69 | beijing | | 1003 | Cerry | 14 | jiangsu | +------+-------+------+---------+ 2 rows in set (0.00 sec) |
在進行分組及排序操作前，先插入幾條資料
1 2 3 4 5 6 7 | student1 = Student(id=1001, name='Alice', age=22, address='beijing') student2 = Student(id=1004, name='Dany', age=14, address='beijing') student3 = Student(id=1005, name='Ever', age=97, address='beijing') student4 = Student(id=1006, name='For', age=50, address='beijing') session.add_all([student1, student2, student3, student4]) session.commit() session.close() |
資料庫結果確認
1 2 3 4 5 6 7 8 9 10 11 12 | mysql> select * from student; +------+-------+------+---------+ | id | name | age | address | +------+-------+------+---------+ | 1001 | Alice | 22 | beijing | | 1002 | Bob | 69 | beijing | | 1003 | Cerry | 14 | jiangsu | | 1004 | Dany | 14 | beijing | | 1005 | Ever | 97 | beijing | | 1006 | For | 50 | beijing | +------+-------+------+---------+ 6 rows in set (0.00 sec) |
統計
統計方法為count()
1 2 | count_student = session.query(Student).filter(Student.name.like('%e%')).count() print("姓名中帶字母e的人{0}個".format(count_student)) |
輸出結果
1
| 姓名中帶字母e的人3個
|
分組
分組方法為group_by()
1 2 3 | group_student = session.query(Student).group_by(Student.address).all() for i in group_student: print(i.id, i.name, i.age, i.address) |
輸出結果
1 2 | 1001 Alice 22 beijing 1003 Cerry 14 jiangsu |
排序
排序方法為order_by()，預設為升序，反序在order_by裡面使用desc()方法。
1 2 3 4 5 6 7 8 9 | order_student = session.query(Student).filter(Student.age > 30).order_by(Student.age).all() print("預設排序輸出") for x in order_student: |