erDiagram
  direction LR

  tb_major ||--o{ tb_course : contains
  tb_major ||--o{ tb_major_lead : maps
  tb_course ||--o{ tb_course_resource : owns
  tb_major ||--o{ tb_course_resource : constrains
  tb_course_resource ||--|| tb_course_resource_best : marks
  tb_course_resource ||--o{ tb_course_resource_log : logs
  tb_course_resource ||--o{ tb_cr_user_score : scores

  tb_major {
    bigint major_id PK
    varchar name UK
  }

  tb_major_lead {
    bigint major_id PK
    bigint user_id PK
  }

  tb_course {
    bigint course_id PK
    bigint major_id FK
    varchar name
  }

  tb_course_resource {
    bigint resource_id PK
    bigint major_id FK
    bigint course_id FK
    bigint uploader_id FK
    varchar resource_type
    varchar status
  }

  tb_course_resource_best {
    bigint resource_id PK
  }

  tb_course_resource_log {
    bigint log_id PK
    bigint resource_id FK
    bigint operator_id FK
  }

  tb_cr_user_score {
    bigint id PK
    bigint resource_id FK
    bigint user_id FK
    int score
  }