级联: class Witer(db.Model): books=db.relationship('writer',cascade='save-update,merge,delete')
all all,delete-orphan
事件监听: set append remove init_scalar init_collection
@db.event.listens_for(Post.body,'set') def increment_edit_time(target,value,oldvalue,initiator): if target.edit_time is not None: target.edit_time+=1
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