[英]How to query a one to many/many to many relationship in Flask SQL Alchemy?
[英]How to do a many to many query in Flask-SQL Alchemy?
我正在使用Flask和SQL-Alchemy为我的Android应用程序创建API。 我有一个MySQL数据库,其表设置如下:
symptoms:
| _id | symptom |
food_categories:
| _id | food_categories |
food_recommendation_type:
| _id | food_categories |
symptom_food_relationship: (This table is association table relating all three)
| id | symptom_id | food_category_id | food_recommendation_type_id |
在我的Flask应用程序中,我已映射出每个表:
symptom_food_relationship_table = db.Table('symptom_food_relationship',
db.Column('id', db.Integer),
db.Column('symptom_id', db.Integer, ForeignKey('symptoms._id')),
db.Column('food_category_id', db.Integer, ForeignKey('food_categories._id')),
db.Column('food_recommendation_type_id', db.Integer, ForeignKey('food_recommendation_type._id')))
class Symptom(db.Model):
__tablename__ = 'symptoms'
_id = db.Column(db.Integer, primary_key=True)
symptom = db.Column(db.String(100))
symptom_food_relationship = relationship("Food_Categories",
secondary=symptom_food_relationship_table)
class Food_Categories(db.Model):
__tablename__ = 'food_categories'
_id = db.Column(db.Integer, primary_key=True)
food_categories = db.Column(db.String(30))
class Food_Recommendation_Type(db.Model):
__tablename__ = 'food_recommendation_type'
_id = db.Column(db.Integer, primary_key=True)
food_recommendation_type = db.Column(db.String)
该表如下所示:
id symptom_id food_categoryid food_recommendation_id
1 1 2 1
11 1 8 1
21 1 0 3
31 1 3 3
我的问题是将这些值更改为其名称的查询。 要查询一张表,我会说结果= Symptom.query.all()。 我知道执行此操作的SQL语句是...
SELECT s.symptom, fc.food_categories, fr.food_recommendation_type
FROM symptoms AS s
INNER JOIN symptom_food_relationship AS srt
INNER JOIN food_categories AS fc
INNER JOIN food_recommendation_type AS fr
ON s._id = srt.symptom_id
AND fc._id = srt.food_category_id
AND fr._id = srt.food_recommendation_type_id
WHERE s._id='1'
ORDER BY s.symptom, food_categories
什么是等效的SQL炼金术查询语句。 因此,我可以在JSON响应中构建它。
您想提出这样的事情:
results = (session.query(Symptom)
.join(Symptom. symptom_food_relationship)
.values(Symptom.symptom,
Food_Categories. food_categories,
Food_Recommendation_Type.food_recommendation_type))
结果以某种方式收集:
resultlist = []
for username, message, time in results:
resultlist.append({'symptom': symptom,
'food_categories': food_categories,
'food_recommendation_type': food_recommendation_type})
可能会有更优雅的方法来处理您的数据结构,但是这种方法应该可行。
最好的方法是阅读有关此问题的文档: http : //docs.sqlalchemy.org/en/rel_0_9/orm/query.html#sqlalchemy.orm.query.Query.join
祝好运 :)
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