postgresql 如何自动填充 SQLAlchemy 数据库字段？(Flask-SQLAlchemy)
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How Can I Automatically Populate SQLAlchemy Database Fields? (Flask-SQLAlchemy)
提问by rdegges
I've got a simple User model, defined like so:
我有一个简单的 User 模型，定义如下：
# models.py
from datetime import datetime
from myapp import db
class User(db.Model):
id = db.Column(db.Integer(), primary_key=True)
email = db.Column(db.String(100), unique=True)
password = db.Column(db.String(100))
date_updated = db.Column(db.DateTime())
def __init__(self, email, password, date_updated=None):
self.email = email
self.password = password
self.date_updated = datetime.utcnow()
When I create a new User object, my date_updatedfield gets set to the current time. What I'd like to do is make it so that wheneverI save changes to my User object my date_updatedfield is set to the current time automatically.
当我创建一个新的 User 对象时，我的date_updated字段被设置为当前时间。我想要做的是，每当我保存对用户对象的更改时，我的date_updated字段都会自动设置为当前时间。
I've scoured the documentation, but for the life of me I can't seem to find any references to this. I'm very new to SQLAlchemy, so I really have no prior experience to draw from.
我已经搜索了文档，但是对于我的一生，我似乎找不到任何对此的引用。我对 SQLAlchemy 很陌生，所以我真的没有经验可以借鉴。
Would love some feedback, thank you.
希望得到一些反馈，谢谢。
回答by plaes
Just add server_defaultor defaultargument to the column fields:
只需向列字段添加server_default或default参数：
created_on = db.Column(db.DateTime, server_default=db.func.now())
updated_on = db.Column(db.DateTime, server_default=db.func.now(), server_onupdate=db.func.now())
I prefer the {created,updated}_oncolumn names. ;)
我更喜欢{created,updated}_on列名。;)
SQLAlchemy docs about column insert/update defaults.
SQLAlchemy 文档关于列插入/更新默认值。
[Edit]:Updated code to use server_defaultarguments in the code.
[编辑]：更新了代码以server_default在代码中使用参数。
[Edit 2]:Replaced onupdatewith server_onupdatearguments.
[编辑 2]：替换onupdate为server_onupdate参数。
回答by Savad KP
date_created = db.Column(db.DateTime, default=db.func.current_timestamp())
date_modified = db.Column(db.DateTime, default=db.func.current_timestamp(),
onupdate=db.func.current_timestamp())
