增加了num的唯一键，修改了dao和api

class_management/database.py

@@ -11,14 +11,13 @@ DB_HOST = os.getenv("DB_HOST", "localhost")
 DB_PORT = os.getenv("DB_PORT", "3306")
 DB_NAME = os.getenv("DB_NAME", "student_manage_system")
 
-class_management_rul = f"mysql+pymysql://{DB_USER}:{DB_PASSWORD}@{DB_HOST}:{DB_PORT}/{DB_NAME}?charset=utf8mb4"
+class_management_url = "mysql+pymysql://root:123456@localhost:3306/student_manage_system?charset=utf8mb4"
 
-engine = create_engine(class_management_rul)
+engine = create_engine(class_management_url)
 SessionLocal = sessionmaker(bind=engine,autocommit=False, autoflush=False)
 Base = declarative_base()
 
 # 获取数据库会话依赖
-
 def get_db():
     db = SessionLocal()
     try :