sqlalchemy执行sql语句

#删除user表中的所有数据,表中的自增字段又从默认值开始
session.execute("truncate table user")

mysql语句查看表结构详细信息

desc table_name 语句:

如:(查看person表的结构)

desc person;
+-------+------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(8) | YES | MUL | NULL | |
+-------+------------+------+-----+---------+----------------+ sqlalchemy 模型与表的映射
class Article(db.Model):
__tablename__='article'
id=db.Column(db.Integer,primary_key=True,autoincrement=True)
title=db.Column(db.String(100),nullable=False)
content=db.Column(db.Text,nullable=False)
db.create_all()
+---------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| title | varchar(100) | NO | | NULL | |
| content | text | NO | | NULL | |
+---------+--------------+------+-----+---------+----------------+

### FLask -SQLALchemy数据的增、删、改、查:
1.增:
#增加:
article1 = Article(title=' aaa' , content= ' bbb')
db. session. add(article1)
#事务
db. session. commit()

2.查:
# select * from article where article.title='aaa' ;
article1 = Article. query. filter(Article.title == 'aaa').first()
print (article1. title)

3.改:
# 1.先把你要更改的数据查找出来
article1 = Article. query. filter(Article.title == 'aaa'). first()
# 2.把这条数据,你需要修改的地方进行修改
article1.title = 'new title '
# 3.做事务的提交
db. session. commit( )

4.删:
# 1.把需要删除的数据查找出来
article1 = Article. query. filter(Article.content == 'bbb'). first()
# 2.把这条数据删除掉
db. session. delete(article1)
# 3.做事务提交
db. session. commit( )

### Flask- SQLALchemy外键及其关系:

1.外键:

class User(db. Model):
__tablename__ ='user'
id = db.Column(db.Integer, primary_ key=True, autoincrement=True)
username = db.Column(db.String(100) ,nullable=False) class Article( db.Model):
__tablename__ ='article'
id = db.Column( db.Integer, primary_ key=True, autoincrement=True)
title = db.Column(db.String(100) , nullable=False)
content = db.Column(db.Text, nullable=False)
author_id = db.Column(db.Integer, db.ForeignKey('user.id')
author = db.relationship( 'User' , backref=db.backref( 'articles'))

2.  author = db. relationship( 'User', backref=db. backref('articles'))

解释:
*   给'Article'这个模型添加一个'author'属性,可以访问这篇文章的作者的数据,像访问普通模型一样。
*   'backref'是定义反向引用,可以通过'User.articles'访问这个模型所写的所有文章。

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