从flask

本文介绍了从flask-sqlalchemy中的联接查询中读取的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

在成功连接两个数据库表之后，我试图通过寻址第一个表来从第二个表中读取数据.我正在从jinja2模板中寻址opinion.topic_name，但未返回任何内容. 如何从加入的查询中访问Topic.topic_name值?

After successfully joining two db tables, I'm trying to read the data from the 2nd table by addressing the first. I'm addressing opinion.topic_name from my jinja2 template, but nothing is returned. How can I access the Topic.topic_name value from the joined query?

@main.route('/', methods=['GET', 'POST']) def index(): form = IndexForm() opinions = [] if form.validate_on_submit(): opinions = Opinion.query .filter_by(party_id=form.party.data) .filter_by(topic_id=form.topic.data) .join('topic') .all() return render_template('index.html', form=form, opinions=opinions)

模型

class Opinion(db.Model): id = db.Column(db.Integer, primary_key=True) text = db.Column(db.String(2000)) topic_id = db.Column(db.Integer, db.ForeignKey('topic.id')) party_id = db.Column(db.Integer, db.ForeignKey('party.id')) class Topic(db.Model): id = db.Column(db.Integer, primary_key=True) topic_name = db.Column(db.String(64)) opinions = db.relationship(Opinion, backref='topic')

模板(jinja2)

<div> {{ wtf.quick_form(form) }} </div> <div> {% for opinion in opinions %} <div class='jumbotron'> <h1>{{ opinion.topic_name }}</h1> <p>{{ opinion.text }}</p> </div> {% endfor %} </div>

推荐答案

此查询:

opinions = Opinion.query .filter_by(party_id=form.party.data) .filter_by(topic_id=form.topic.data) .join(Topic) .all()

将返回Opinion模型的列表，并且由于在Topic模型中的关系中，您将其定义为:

will return a list of Opinion models and since in your relationship in Topic model, you defined it as:

opinions = db.relationship(Opinion, backref='topic')

然后，在jinja2模板中访问Topic.topic_name，您应该执行以下操作:

Then, in your jinja2 template, to access Topic.topic_name, you should do:

<h1>{{ opinion.topic.topic_name }}</h1>