diff --git a/4/4.py b/4/4.py
new file mode 100644
index 0000000..64d0056
--- /dev/null
+++ b/4/4.py
@@ -0,0 +1,95 @@
+from sqlalchemy import (
+    create_engine,
+    Column,
+    Integer,
+    String,
+    ForeignKey,
+    DateTime
+)
+from sqlalchemy.orm import declarative_base, relationship, sessionmaker
+from datetime import datetime
+
+DATABASE_URL = "sqlite:///files.db"
+
+engine = create_engine(DATABASE_URL, echo=True)
+SessionLocal = sessionmaker(bind=engine)
+Base = declarative_base()
+
+
+class User(Base):
+    __tablename__ = "users"
+
+    id = Column(Integer, primary_key=True)
+    username = Column(String, unique=True, nullable=False)
+
+    files = relationship(
+        "File",
+        back_populates="owner",
+        cascade="all, delete-orphan"
+    )
+
+    def __repr__(self):
+        return f"<User id={self.id} username={self.username}>"
+
+
+class File(Base):
+    __tablename__ = "files"
+
+    id = Column(Integer, primary_key=True)
+    filename = Column(String, nullable=False)
+    path = Column(String, nullable=False)
+    uploaded_at = Column(DateTime, default=datetime.utcnow)
+
+    owner_id = Column(Integer, ForeignKey("users.id"))
+    owner = relationship("User", back_populates="files")
+
+    def __repr__(self):
+        return f"<File id={self.id} filename={self.filename}>"
+
+
+def run_migration():
+    Base.metadata.create_all(bind=engine)
+    print("Migration successful")
+
+
+def crud_test():
+    db = SessionLocal()
+
+    user = User(username="fatemeh")
+    db.add(user)
+    db.commit()
+    db.refresh(user)
+
+    file1 = File(
+        filename="report.pdf",
+        path="/uploads/report.pdf",
+        owner=user
+    )
+
+    db.add(file1)
+    db.commit()
+
+    users = db.query(User).all()
+    files = db.query(File).all()
+
+    print("Users:", users)
+    print("Files:", files)
+
+    file1.filename = "final_report.pdf"
+    db.commit()
+
+    updated_file = db.query(File).first()
+    print("Updated file:", updated_file)
+
+    db.delete(user)
+    db.commit()
+
+    remaining_files = db.query(File).all()
+    print("Remaining files:", remaining_files)
+
+    db.close()
+
+
+if __name__ == "__main__":
+    run_migration()
+    crud_test()