flask中使用sqlalchemy处理多对多 · 常用笔记

# flask中使用sqlalchemy处理多对多 ``` <pre class="calibre29">``` from flask import Flask from flask_sqlalchemy import SQLAlchemy import config #以上导入所需模块 app = Flask(__name__) #实例化flask app.config.from_object(config)#引入数据库配置 db = SQLAlchemy(app) #实例化sqlalchemy #首先创建三张表 #最后创建中间表 article_tag = db.Table('article_tag',db.Column('article_id',db.Integer,db.ForeignKey('article.id'),primary_key=True), db.Column('tag_id',db.Integer,db.ForeignKey('tag.id'),primary_key=True)) #第一创建article表 class Article(db.Model): __tablename__ = 'article' id = db.Column(db.Integer,primary_key=True,autoincrement=True) title = db.Column(db.String(100),nullable=False) #两张表进行关联 tags = db.relationship('Tag',secondary =article_tag,backref = db.backref('articles') ) #第二创建标签表 class Tag(db.Model): __tablename__ = 'tag' id = db.Column(db.Integer, primary_key=True, autoincrement=True) name = db.Column(db.String(100), nullable=False) #标签名字 db.create_all() @app.route('/') def index(): article1 = Article(title = 'aaa') article2 = Article(title = 'bbb') tag1 = Tag(name = '111') tag2= Tag(name = '222') #对文章添加标签 article1 .tags.append(tag1) article1 .tags.append(tag2) article2 .tags.append(tag1) article2 .tags.append(tag2) db.session.add(article1) db.session.add(article2) db.session.add(tag1) db.session.add(tag2) db.session.commit() return 'hello' if __name__ == '__main__': app.run(debug=True) ``` ``` 查看多对多数据 ``` <pre class="calibre14">``` from flask import Flask from flask_sqlalchemy import SQLAlchemy import config #以上导入所需模块 app = Flask(__name__) #实例化flask app.config.from_object(config)#引入数据库配置 db = SQLAlchemy(app) #实例化sqlalchemy #首先创建三张表 #最后创建中间表 article_tag = db.Table('article_tag',db.Column('article_id',db.Integer,db.ForeignKey('article.id'),primary_key=True), db.Column('tag_id',db.Integer,db.ForeignKey('tag.id'),primary_key=True)) #第一创建article表 class Article(db.Model): __tablename__ = 'article' id = db.Column(db.Integer,primary_key=True,autoincrement=True) title = db.Column(db.String(100),nullable=False) #两张表进行关联 tags = db.relationship('Tag',secondary =article_tag,backref = db.backref('articles') ) #第二创建标签表 class Tag(db.Model): __tablename__ = 'tag' id = db.Column(db.Integer, primary_key=True, autoincrement=True) name = db.Column(db.String(100), nullable=False) #标签名字 db.create_all() @app.route('/') def index(): # article1 = Article(title = 'aaa') # article2 = Article(title = 'bbb') # # tag1 = Tag(name = '111') # tag2= Tag(name = '222') # # #对文章添加标签 # article1 .tags.append(tag1) # article1 .tags.append(tag2) # article2 .tags.append(tag1) # article2 .tags.append(tag2) # # db.session.add(article1) # db.session.add(article2) # db.session.add(tag1) # db.session.add(tag2) # db.session.commit() #查看标题是aa的有哪些文章 article1 = Article.query.filter(Article.title == 'aaa').first() tags = article1.tags for tag in tags: print(tag.name ) return 'hello' if __name__ == '__main__': app.run(debug=True) ``` ```