以下所有代码片段都使用了统一的引用，该引用如下：
from sqlalchemy import create_engine, ForeignKey from sqlalchemy.ext.declarative import declarative_base from sqlalchemy import Column, String, Integer, Table from sqlalchemy.orm import relationship, sessionmaker
表结构设计：
engine = create_engine("mysql+pymysql://root:[email protected]/study?charset=utf8", echo=True) # 连接数据库,显示SQL语句 Base = declarative_base() # 创建基类 class Student(Base): __tablename__ = ‘students‘ # 指定表名 __table_args__ = { # "mysql_engine":"MyISAM", "mysql_charset":"utf8" } # show create table students 可以查看建表语句;默认是Innodb,lating-1.如果想显示中文需要修改指定建表的类型,同时,engine也要指定编码格式 id = Column(Integer, primary_key=True) name = Column(String(30)) gender = Column(Integer) std_id = Column(String(10)) teacher = Column(String(30)) def __str__(self): return self.name Base.metadata.create_all(engine) # 创建所有继承自 Base 的类对应的表
sqlslchemy在数据库中创建表之前，会先检查该表是否存在，如果不存在，才会去创建新表。
class Student(Base): __tablename__ = ‘students‘ # 指定表名 id = Column(Integer, primary_key=True) name = Column(String(30)) gender = Column(Integer) std_id = Column(String(10)) teacher = Column(String(30)) **math = Column(Integer)** def __str__(self): return self.name
虽然新加了一个math 变量（字段），但是由于数据库中已有students表，所以不会去创建新表，match字段也就不存在。
插入数据
Session = sessionmaker(bind=engine) # 获取 Session类 ses = Session() # 获取session对象 zhangsan = Student(name="zhangsan", gender=1, std_id=‘XS331‘, teacher=‘hanmeimei‘, math=90) lisi = Student(name="lisi", gender=1, std_id=‘XS332‘, teacher=‘hanmeimei‘, math=10) wangwu = Student(name="wangwu", gender=0, std_id=‘XS333‘, teacher=‘lilei‘, math=60) zhaoliu = Student(name="zhaoliu", gender=0, std_id=‘XS337‘, teacher=‘lilei‘, math=80) ses.add(zhangsan) # 单条添加 ses.add_all([lisi, wangwu, zhaoliu]) # 批量添加 ses.commit()
修改数据
zhangsan = ses.query(Student).filter_by(name=‘zhangsan‘).first() zhangsan.math = 91 ses.commit()
也可以在还创建数据的时候修改：
liqi = Student(name="liqi", gender=1, std_id=‘XS335‘, teacher=‘xiadonghai‘, math=100) ses.add(liqi) liqi = ses.query(Student).filter_by(name=‘liqi‘).first() liqi.gender = 0 ses.commit()
liqi = Student(name="liqi", gender=1, std_id=‘XS335‘, teacher=‘xiadonghai‘, math=100) liqi.gender = 0 ses.add(liqi) ses.commit()
sess.query(Student).filter_by(name=‘liming‘).update({‘gender‘:0}) sess.commit()
删除
# result = sess.query(Student).filter(Student.id == 1 ).delete() # sess.commit() # result = sess.query(Student).filter(Student.id == 2 ).first() # sess.delete(result) # sess.commit()
查询
# = 操作符 # students_99 = sess.query(Student).filter_by(name =‘zhangsan‘).all() # students_100 = sess.query(Student).filter(Student.name == ‘zhangsan‘).all() # for i in students_100: # print(i.name) # ！= 操作符 # student_101 = sess.query(Student).filter_by(name != ‘liming‘).all() # error # student_98 = sess.query(Student).filter(Student.name != ‘liming‘).all() # for i in student_98: # print(i.name) # > ,<, <=, >=, 操作符 # student_60 = sess.query(Student).filter(Student.math > 10).all() # student_61= sess.query(Student).filter_by(math>10).all() # error # student_62 = sess.query(Student).filter(Student.math < 100).all() # student_63 = sess.query(Student).filter(Student.math <= 90).all() # student_64 = sess.query(Student).filter(Student.math >= 90).all() # student_64 = sess.query(Student).filter(Student.math <> 90).all() # error # for i in student_60: # print(i.math) # for i in student_62: # print(i.math) # for i in student_63: # print(i.math) # for i in student_64: # print(i.math) # 根据主键获取对象 # students_1 = sess.query(Student).get(1) # print(students_1 # value指定要获取的字段 返回的是生成器 # students_3 = sess.query(Student).value(Student.name) # print(students_3) # values 指定多个字段 返回的是生成器 # students_3_2 = sess.query(Student).values(Student.id,Student.name) # print(students_3_2) # for i in students_3_2: # print(i) # 一次获取多个字段值 # students_4 = sess.query(Student.name,Student.gender).all() # print(students_4) # for i in students_4: # print(i) # 后续添加的方式选择要得到的字段结果 # students_5 = sess.query(Student.name).add_columns(Student.gender).all() # print(students_5) # student_6 = sess.query(Student).filter_by(name="王大麻子").one() # print(student_6) # 字段别名 # student_7 = sess.query(Student.name.label(‘std_name‘)).all() # print(student_7) # for i in student_7: # print(i.std_name) # print(i[0]) # 第二种取值方式 # student_8 = sess.query(Student.name).all() # print(student_8) # for i in student_8: # print(i.name) # print(i[0]) # 分页 # student_10 = sess.query(Student).limit(2).offset(1).all() # student_11 = sess.query(Student).offset(1).limit(2).all() # student_12 = sess.query(Student)[1:3] # for i in student_10: # print(i.id) # for i in student_11: # print(i.id) # for i in student_12: # print(i.id) # filter 和 filter_by # student_13 = sess.query(Student).filter_by(id=1).one_or_none() # student_14 = sess.query(Student).filter(Student.id == 1).one_or_none() # print(student_13) # print(student_14) # chain 链式调用 # student_15 = sess.query(Student).filter_by(gender=1).filter(Student.math>80).all() # # student_15_2 = sess.query(Student).filter_by(gender=1).filter_by(math>80).all() # error # student_16 = sess.query(Student).filter(Student.gender == 1).filter(Student.math>80).all() # for i in student_15: # print(i.name) # for i in student_16: # print(i.name) # like 操作符 % 代表任意多个字符 _ 代表一个字符 # student_17 = sess.query(Student).filter(Student.name.like("%i%")).all() # for i in student_17: # print(i.name) # student_17_2 = sess.query(Student).filter(Student.name.like("%i_i")).all() # for i in student_17_2: # print(i.name) # not like # student_70 = sess.query(Student).filter(~Student.name.like("%i_i")).all() # student_71 = sess.query(Student).filter(Student.name.notlike("%i_i")).all() # for i in student_70: # print(i.name) # print(student_70 == student_71) # in 操作符 # student_18 = sess.query(Student).filter(Student.name.in_([‘zhangsan‘,‘lisi‘,‘wangwu‘])).all() # for i in student_18: # print(i.name) # not in # student_19 = sess.query(Student).filter(~Student.name.in_([‘lisi‘])).all() # student_19_2 = sess.query(Student).filter(Student.name.notin_([‘lisi‘])).all() # for i in student_19: # print(i.name) # print(student_19 == student_19_2) # 是否为null # student_20 = sess.query(Student).filter(Student.name != None).all() # student_21 = sess.query(Student).filter(~Student.name.is_(None)).all() # student_22 = sess.query(Student).filter(Student.name.isnot(None)).all() # student_21_3 = sess.query(Student).filter(Student.name.is_(‘zhangsan‘)).all() # error # student_21_2 = sess.query(Student).filter(Student.name.is_(1)).all() # for i in student_20: # print(i.name) # print(student_20 == student_21 == student_22) # student_23 = sess.query(Student).filter(Student.math.is_(90)).all() # student_24 = sess.query(Student).filter(Student.math == None).all() # 类别名 # flower = aliased(Student) # student_9 = sess.query(flower.name).all() # print(student_9) # and # student_25 = sess.query(Student).filter(Student.gender == 1, Student.math > 70).all() # student_26 = sess.query(Student).filter(and_(Student.gender == 1, Student.math > 70)).all() # 别忘了引入该方法 # student_27 = sess.query(Student).filter(Student.gender == 1).filter(Student.math > 70).all() # for i in student_25: # print(i.name) # print(student_25 == student_26 == student_27) # or # student_28 = sess.query(Student).filter(or_(Student.gender == 1, Student.math > 80)).all() # for i in student_28: # print(i.name) # 错误用法 # error_1 = sess.query(Student).filter_by(and_(Student.id == 1, Student.name == ‘lisi‘)).first() # error_2 = sess.query(Student).filter_by(and_(id=1, name=‘lisi‘)).first() # error_3 = sess.query(Student).filter(and_(id=1, name=‘lisi‘)).first() # one 有且只有一个，否则报错 # student_30 = sess.query(Student).filter(Student.id == 1).one() # print(student_30) # 可以只有一个或者没有，不能为多个结果，否则报错 # student_31 = sess.query(Student).filter(Student.id == 10).one_or_none() # print(student_31) # text 原生sql条件语句 # student_31 = sess.query(Student).filter(text("name=‘lisi‘")).first() # 注意值为字符串时的写法 # student_32 = sess.query(Student).filter(text("id=1")).first() # 注意值为 数字 的写法 # student_31 = sess.query(Student).filter(text("id>1 and math>10")).all() # for i in student_31: # print(i.name) # order_by 排序 # student_33 = sess.query(Student).filter(text("math >= 10")).order_by(~text("math")).all() # 逆序 # student_33_2 = sess.query(Student).filter(text("math >= 10")).order_by(text("math")).all() # 顺序 # student_33_2_1 = sess.query(Student).filter(text("math >= 10")).order_by(desc(text("math"))).all() # 逆序 # student_33_3 = sess.query(Student).order_by(desc(Student.math)).all() # 逆序 # student_33_4 = sess.query(Student).order_by(Student.math.desc()).all() # 逆序 # student_33_5 = sess.query(Student).order_by(~Student.math).all() # 逆序 # student_33_6 = sess.query(Student).order_by(Student.math).all() # 顺序 # print(student_31) # print(student_32) # print("___"* 30) # for i in student_33: # print(i.math) # print("___"* 30) # for i in student_33_2: # print(i.math) # for i in student_33_3: # print(i.math) # for i in student_33_4: # print(i.math) # for i in student_33_5: # print(i.math) # for i in student_33_6: # print(i.math) # text 插入变量 # student_34 =sess.query(Student).filter(text("gender=:sex and math>:score")).params(sex=1, score=1).all() # for i in student_34: # print(i.name) # from_statement 原生sql语句 # student_35 = sess.query(Student).from_statement(text("select * from students where id=:id")).params(id=1).one() # student_36 = sess.query(Student).from_statement("select * from students where math>:score").params(score=10).all() # student_36_1 = sess.query(Student).from_statement("select * from students where math>10").all() # print(student_35) # for i in student_36: # print(i.name) # print(student_36 == student_36_1) # count # student_38 = sess.query(Student).filter_by(gender=1).count() # student_38_2 = sess.query(func.count(Student.name),Student.name).group_by(Student.name).all() # student_38_3 = sess.query(func.count(Student.name),Student.gender).group_by(Student.gender).all() # print(student_38_2) # print(student_38_3) # group_by 分组 # student_39 = sess.query(Student).group_by(Student.gender == 1).count() # print(student_39) # having # student_39_1 = sess.query(Student).group_by(Student.gender == 1).having(Student.math>60).all() # for i in student_39_1: # print(i) # distinct # student_40 = sess.query(distinct(Student.name)).all() # for i in student_40: # print(i)