notice
- id - pk, int, autoinc-
- title - varchar , nn
- author - varchar, nn
- subject - varchar , nn
- deadline - timestamp, nn
- created_at - timestamp, nn
- updated_at - timestamp, default: null
user
- id - pk, varchar
- pwd - varchar, nn
- class - varchar, nn
- name - varchar, nn
- authority - varchar (user, manager, super), default : user
- position - varchar, nn
- created_at - timestamp, nn
- updated_at - timestamp, default: null
affiliation