SQLAlchemy增删改查

# flask中使用SQL alchemy------------------------------------------
from flask_sqlalchemy import SQLAlchemy
from flask import Flask


app = Flask(__name__)

# app.config["SQLALCHEMY_DATABASE_URI"] = "mysql+pymysql://root:[email protected]:3306/test"

app.config["SQLALCHEMY_DATABASE_URI"] = "sqlite:///" + "/home/lmp/sql/first.db"
app.config["SQLALCHEMY_TRACK_MODIFICATIONS"] = False
app.config["SECRET_KEY"] = "sfjlewjlxjfhal234l2jfsldfj"

db = SQLAlchemy(app)

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# 增
t = Table()    # 模型类实例化
t1 = Table() 
t2 = Table() 
db.session.add(t)   # 增加一条
db.session.commit()

db.session.add_all([t, t1, t2])  # 增加多条
db.sesion.commit()

# 查  -----------------------------------------------------------------
# 查一个 get()
raw = table.query.get(id)

# 查全部 all()
raws = table.query.all()    # 返回列表

# 条件查询 filter()
raws = table.query.filter(table.id>=100)
raw = table.query.filter(table.id>=100).first()

raws = table.query.filter_by(name="xx").all()
raw = table.query.filter_by(name="xx").first()
raw = table.query.filter_by(name="xx").filter(table.id==2)

# 从1查到多
raws = table.query.get(1)   # 返回的是一个列表，列表中的每一元素都是副表的对象
for raw in raws:
      print(raw.field)

# 从多查到1
raw = table.query.filter(grade=="100").first()
print(raw.backref.id)
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# 改
方法一：  
修改一条
change_nums = table.query.get(1).update({"field": "value"})
db.session.commit()

批量修改 
change_nums = table.query.filter(id>10).update({"field": "value"})
db.session.commit()

raws = table.query.filter(id>10).first()
raw.name = "hello"
db.session.commit()
-----------------------------------------------------------------------

# 删除
delete_nums = table.query.filter(id>10).delete() 

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## 建表
# 学生表
class Student(db.Model):
       __tablename__ = "student"
       id = db.Column(db.Integer, primary_key=True)  # 主键
       name = db.Column(db.String(64), nullable=False)  # 学生姓名  不能为空
       gender = db.Column(db.Enum("男", "女"), nullable=False)  不能为空
       phone = db.Column(db.String(11))  # 手机号   可以为空
       grades = db.relationship("Grade", backref="course")


# 课程表
class Course(db.Model):
       __tablename__ = "course"
      id = db.Column(db.Integer, primary_key=True)  # 主键
      name = db.Column(db.String(64), nullable=False)  # 课程名
       

# 教师表
class Teacher(db.Model):
       __tablename__ = "teacher"
      id = db.Column(db.Integer, primary_key=True)  # 主键
      name = db.Column(db.String(64), nullable=False)  # 老师名
      gender = db.Column(db.Enum("男", "女"), nullable=False)
      phone = db.Column(db.String(11))

# 成绩表
class Grade(db.Model):
       __tablename__ = "grade"
       id = db.Column(db.Integer, primary_key=True)  # 主键
       grade = db.Column(db.String(3), nullable=False)
       student_id = db.Column(db.Integer, db.ForeignKey("student.id"))