增加了num的唯一键，修改了dao和api

class_management/database.py

@@ -3,25 +3,24 @@ from sqlalchemy.orm import sessionmaker,declarative_base
 
 
 # 导入.env参数
-import os
-from dotenv import load_dotenv
-load_dotenv( )
-DB_USER = os.getenv("DB_USER", "root")
-DB_PASSWORD = os.getenv("DB_PASSWORD", "")
-DB_HOST = os.getenv("DB_HOST", "localhost")
-DB_PORT = os.getenv("DB_PORT", "3306")
-DB_NAME = os.getenv("DB_NAME", "student_manage_system")
+# import os
+# from dotenv import load_dotenv
+# load_dotenv( )
+# DB_USER = os.getenv("DB_USER", "root")
+# DB_PASSWORD = os.getenv("DB_PASSWORD", "")
+# 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_url = f"mysql+pymysql://{DB_USER}:{DB_PASSWORD}@{DB_HOST}:{DB_PORT}/{DB_NAME}?charset=utf8mb4"
 
-class_management_url = 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"
+class_management_url = "mysql+pymysql://root:123456@localhost:3306/student_manage_system?charset=utf8mb4"
 
 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 :