sqlalchemy執行sql語句

#刪除user表中的所有數據，表中的自增字段又從默認值開始
session.execute("truncate table user")

 

mysql語句查看表結構詳細信息

desc table_name 語句：

如：（查看person表的結構）

desc person;
+-------+------------+------+-----+---------+----------------+
| Field | Type       | Null | Key | Default | Extra          |
+-------+------------+------+-----+---------+----------------+
| id    | int(11)    | NO   | PRI | NULL    | auto_increment |
| name  | varchar(8) | YES  | MUL | NULL    |                |
+-------+------------+------+-----+---------+----------------+

sqlalchemy 模型與表的映射

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數據的增、刪、改、查:
1.增:
#增加:
article1 = Article(title=' aaa' , content= ' bbb')
db. session. add(article1)
#事務
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.先把你要更改的數據查找出來
article1 = Article. query. filter(Article.title == 'aaa'). first()
# 2.把這條數據，你需要修改的地方進行修改
article1.title = 'new title '
# 3.做事務的提交
db. session. commit( )

 

4.刪:
# 1.把需要刪除的數據查找出來
article1 = Article. query. filter(Article.content == 'bbb'). first()
# 2.把這條數據刪除掉
db. session. delete(article1)
# 3.做事務提交
db. session. commit( )

 

### Flask- SQLALchemy外鍵及其關系:

1.外鍵:

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'))

解釋:
*   給'Article'這個模型添加一個'author'屬性，可以訪問這篇文章的作者的數據，像訪問普通模型一樣。
*   'backref'是定義反向引用，可以通過'User.articles'訪問這個模型所寫的所有文章。