1. 接上一篇 初始sqlalchemy介绍中 我们创建了一个user,student,school,girl,boy表,接下来我们要对那个表进行增删改查
2. 首先需要创建一个数据库的会话
from create_table import engine # 从创建那个模块文件中导入之前创建按的engine
# 创建会话 - 打开数据库链接
from sqlalchemy.orm import sessionmaker
# 1.创建会话窗口
Session = sessionmaker(engine)
# 2.打开会话窗口
db_session = Session()
3.增 增加数据
"""
# 1.增加数据 == insert
# insert into user(name) values("Jack")
"""
from create_table import User
user_obj = User(name='Jack')
# 通过db_session已经打开会话窗口 提交数据
db_session.add(user_obj) # insert into ...
db_session.commit() # 执行会话窗口中的所有操作
db_session.close() # 关闭会话
"""
2. 增加批量
"""
from create_table import User
db_session.add_all([
User(name="Tom"),
User(name="Jeecy"),
User(name="Anney"),
])
db_session.commit()
db_session.close()
# 2.导入学校 学生
from create_table_foreignkey import School, Student
# 3. 添加数据
"""
# 2.添加数据 - 正向 relationship
"""
studen_obj = Student(name="Any",stu2sch=School(name="清华"))
db_session.add(studen_obj)
db_session.commit()
db_session.close()
"""
# 1. 添加数据 - 反向 relationship
"""
school_obj = School(name="北大") # 创建学校
school_obj.sch2stu = [Student(name="Jack"),Student(name="Jeecy")] # 学校关联学生
db_session.add(school_obj)
db_session.commit()
db_session.close()
from create_table_manytomany import Girls, Boys
"""
添加
"""
# 反向添加 通过boy添加girl
boy_obj = Boys(name="Jack")
boy_obj.boy2girl = [Girls(name="Anny"),Girls(name="Lux")]
db_session.add(boy_obj)
db_session.commit()
db_session.close()
# 正向添加 通过girl添加boy
girl_obj = Girls(name="Kaselin",girl2boy=[Boys(name="Yase"),Boys(name="Ezreal")])
db_session.add(girl_obj)
db_session.commit()
db_session.close()
4查 查询数据
- 单表查询
- 常用的简单语句
- db_session.query(User).all()
user表中所有的数据对象
- db_session.query(User).first()
数据库中第一条数据
- db_session.query(User).filter().all()
user表中所有的数据对象
- db_session.query(User).filter(User.id==3).all()
all() 返回就是列表 尽管里面一条数据
- db_session.query(User).filter(User.id==3).first()
返回一条数据
- 条件 >= <=
- user_list = db_session.query(User).filter(User.id >= 3).all()
# 1. 简单查询
# user_list = db_session.query(User).all()
# for row in user_list:
# print(row.id,row.name)
# 2. 查询第一条数据
# user_obj = db_session.query(User).first()
# print(row.id,row.name)
# 3. 待条件的查询
# user_list = db_session.query(User).filter(User.id==3).all()
# print(user_list[0].name)
# 3. 待条件的查询 filter(User.id==3)
# user_list = db_session.query(User).filter(User.id==3).all()
# print(user_list[0].name)
# 4. 不使用表达式 filter_by(id=3)
# user_list = db_session.query(User).filter_by(id=3).all()
# print(user_list[0].name)
#
# user_list = db_session.query(User).filter_by(id=3).first()
# print(user_list.name)
# 5.条件 >= <=
user_list = db_session.query(User).filter(User.id >= 3).all()
print(user_list[0].name)
from create_table_foreignkey import School, Student
"""
1. 正向查询
"""
stu = db_session.query(Student).all()
for row in stu:
print(row.id,row.name,row.school_id,row.stu2sch.name)
"""
2. 反向查询
"""
sch = db_session.query(School).all()
for row in sch:
for row2 in row.sch2stu:
print(row2.id,row2.name,row.id,row.name)
from create_table_manytomany import Girls, Boys
"""
查询
"""
# 正向查询
girl_list = db_session.query(Girls).all()
for girl in girl_list:
for boy in girl.girl2boy:
print(girl.name,boy.name)
# 反向查询
boy_list = db_session.query(Boys).all()
for boy in boy_list:
for girl in boy.boy2girl:
print(boy.name, girl.name)
5. 更新 修改/更新数据
"""
修改数据
要修改数据 先查数据 再修改 保存 提交
sql 语句 update 'user' set 'name'='Jack' where id = 1
"""
from create_table import User
# 1.查询出符合条件的就修改
res = db_session.query(User).filter_by(name="Jeecy").update({"name":"Jeecy222"})
print(res) # res 返回符合查询结果的条数
db_session.commit() # 提交
db_session.close() # 关闭
2. 高级操作
#直接修改
db_session.query(User).filter(User.id > 0).update({"name" : "099"})
#在原有值基础上添加 - 1 提交完之后在更新 防止 原有之基础上更改数据
db_session.query(User).filter(User.id > 0).update({User.name: User.name + "099"}, synchronize_session=False)
#在原有值基础上添加 - 2 原有之基础上 运算
db_session.query(User).filter(User.id > 0).update({"age": User.age + 1}, synchronize_session="evaluate")
'''
正向查询修改 修改Jack学生所在的校区
'''
sch = db_session.query(School).filter(School.name == "清华").first()
db_session.query(Student).filter(Student.name == "Jack").update({"school_id":sch.id})
db_session.commit()
db_session.close()
6 删除
"""
delete user where di = 4
"""
# 删除单条 或者符合条件的
res = db_session.query(User).filter(User.id == 4).delete()
print(res) # 影响行数
db_session.commit()
db_session.close()
''
正向查询修改 删除北大学校所有的学生
'''
sch = db_session.query(School).filter(School.name == "北大").first()
db_session.query(Student).filter(Student.school_id == sch).delete()
db_session.commit()
db_session.close()
7. 附加查询高级查询
- 简单列举 语句
-
from sqlalchemy.sql import and_ , or_ 条件查询
- filter(and_(User.id > 3, User.name == 'Jack'))
-
User.name.label('username') 别名
-
from sqlalchemy.sql import text 筛选
filter(text("id<:value and name=:name")).params(value=224, name='DragonFire').all()
-
filter().order_by(User.id).all() 排序
-
order_by(User.id.desc()) 倒序
-
filter(User.id.between(1, 3)) 大于1 小于 3
-
filter(User.id.in_([1,3,4])) id = [1,3,4]
-
filter(~User.id.in_([1,3,4])) id 不等于 1,3,4
-
filter(User.name.like('e%')) 通配符 模糊查询
from my_create_table import User,engine
from sqlalchemy.orm import sessionmaker
Session = sessionmaker(engine)
db_session = Session()
# 查询数据表操作
# and or
from sqlalchemy.sql import and_ , or_
ret = db_session.query(User).filter(and_(User.id > 3, User.name == 'Jack')).all()
ret = db_session.query(User).filter(or_(User.id < 2, User.name == 'Jack')).all()
# 查询所有数据
r1 = db_session.query(User).all()
# 查询数据 指定查询数据列 加入别名
r2 = db_session.query(User.name.label('username'), User.id).first()
print(r2.id,r2.username) # 15 NBDragon
# 表达式筛选条件
r3 = db_session.query(User).filter(User.name == "Jack").all()
# 原生SQL筛选条件
r4 = db_session.query(User).filter_by(name='Jack').all()
r5 = db_session.query(User).filter_by(name='Jack').first()
# 字符串匹配方式筛选条件 并使用 order_by进行排序
r6 = db_session.query(User).filter(text("id<:value and name=:name")).params(value=224, name='Jack').order_by(User.id).all()
#原生SQL查询
r7 = db_session.query(User).from_statement(text("SELECT * FROM User where name=:name")).params(name='Jack').all()
# 筛选查询列
# query的时候我们不在使用User ORM对象,而是使用User.name来对内容进行选取
user_list = db_session.query(User.name).all()
print(user_list)
for row in user_list:
print(row.name)
# 别名映射 name as nick
user_list = db_session.query(User.name.label("nick")).all()
print(user_list)
for row in user_list:
print(row.nick) # 这里要写别名了
# 筛选条件格式
user_list = db_session.query(User).filter(User.name == "Jack").all()
user_list = db_session.query(User).filter(User.name == "Jack").first()
user_list = db_session.query(User).filter_by(name="Jack").first()
for row in user_list:
print(row.nick)
# 复杂查询
from sqlalchemy.sql import text
user_list = db_session.query(User).filter(text("id<:value and name=:name")).params(value=3,name="Jack")
# 查询语句
from sqlalchemy.sql import text
user_list = db_session.query(User).filter(text("select * from User id<:value and name=:name")).params(value=3,name="Jack")
# 排序 :
user_list = db_session.query(User).order_by(User.id).all()
user_list = db_session.query(User).order_by(User.id.desc()).all()
for row in user_list:
print(row.name,row.id)
#其他查询条件
"""
ret = session.query(User).filter_by(name='Jack').all()
ret = session.query(User).filter(User.id > 1, User.name == 'Jack').all()
ret = session.query(User).filter(User.id.between(1, 3), User.name == 'Jack').all() # between 大于1小于3的
ret = session.query(User).filter(User.id.in_([1,3,4])).all() # in_([1,3,4]) 只查询id等于1,3,4的
ret = session.query(User).filter(~User.id.in_([1,3,4])).all() # ~xxxx.in_([1,3,4]) 查询不等于1,3,4的
ret = session.query(User).filter(User.id.in_(session.query(User.id).filter_by(name='Jack'))).all() 子查询
from sqlalchemy import and_, or_
ret = session.query(User).filter(and_(User.id > 3, User.name == 'Jack')).all()
ret = session.query(User).filter(or_(User.id < 2, User.name == 'Jack')).all()
ret = session.query(User).filter(
or_(
User.id < 2,
and_(User.name == 'eric', User.id > 3),
User.extra != ""
)).all()
# select * from User where id<2 or (name="eric" and id>3) or extra != ""
# 通配符
ret = db_session.query(User).filter(User.name.like('e%')).all()
ret = db_session.query(User).filter(~User.name.like('e%')).all()
# 限制
ret = db_session.query(User)[1:2]
# 排序
ret = db_session.query(User).order_by(User.name.desc()).all()
ret = db_session.query(User).order_by(User.name.desc(), User.id.asc()).all()
# 分组
from sqlalchemy.sql import func
ret = db_session.query(User).group_by(User.extra).all()
ret = db_session.query(
func.max(User.id),
func.sum(User.id),
func.min(User.id)).group_by(User.name).all()
ret = db_session.query(
func.max(User.id),
func.sum(User.id),
func.min(User.id)).group_by(User.name).having(func.min(User.id) >2).all()
"""
# 关闭连接
db_session.close()
