Table: account
 id | integer
 user_id | integer
 password | character varying
 role | character varying
 username | character varying


Table: assignment_rating
 id | integer
 assignment | integer
 rating | integer
 student | integer
 timestamp | timestamp without time zone


Table: book_rating
 id | integer
 book | integer
 rating | integer
 student | integer
 timestamp | timestamp without time zone


Table: category
 id | integer
 parent | integer
 name | character varying


Table: book_subject
 id | integer
 book | integer
 subject | integer


Table: course_subject
 id | integer
 course | integer
 subject | integer


Table: enrollment
 subject | integer
 student | integer
 id | integer
 status | integer
 lesson | integer


Table: lecturer
 id | integer
 account | integer
 name | character varying
 email | character varying


Table: faculty
 id | integer
 name | character
 faculty_describtion | text


Table: friendship
 id | integer
 start | integer
 end | integer


Table: group_discuss
 id | integer
 subject | integer
 type | integer
 group_name | character
 topic | character


Table: lecture_note
 id | integer
 lesson | integer
 title | character
 note_url | text


Table: lecturer_rating
 id | integer
 lecturer | integer
 student | integer
 rating | integer


Table: multimedia
 id | integer
 type | integer
 url | character
 name | character
 author | character varying


Table: note_rating
 id | integer
 rating | integer
 student | integer
 note | integer
 timestamp | timestamp without time zone


Table: multimedia_rating
 id | integer
 rating | integer
 multimedia | integer
 student | integer
 timestamp | timestamp without time zone


Table: multimedia_subject
 multimedia | integer
 subject | integer
 id | integer


Table: note
 chapter | integer
 subject | integer
 student | integer
 id | integer
 type | integer
 content | text


Table: student_preference
 id | integer
 student | integer
 style_preference | integer
 category_preference | integer


Table: subject_requirement
 id | integer
 subject | integer
 pre-requires_subject | integer


Table: student
 account | integer
 course | integer
 last_login | timestamp without time zone
 accumulated_online_time | timestamp without time zone
 id | integer
 email | character varying
 name | character varying
 dob | character varying
 gender | character varying
 nationality | character varying
 occupy | character varying
 graduated_university | character varying


Table: subject
 id | integer
 category | integer
 name | character varying
 thumb | character
 pic | character
 description | character varying


Table: subject_rating
 id | integer
 subject | integer
 student | integer
 rating | integer
 timestamp | timestamp without time zone
 commence | text


Table: subject_tag
 id | integer
 student | integer
 subject | integer
 timestamp | timestamp without time zone
 tag | character


Table: lesson
 id | integer
 year | integer
 lecturer | integer
 subject | integer
 book | integer
 semester | character


Table: assignment
 due_date | date
 id | integer
 lesson | integer
 type | integer
 assignment_task | text


Table: style_preference
 id | integer
 style_preference | character


Table: book
 category | integer
 id | integer
 type | integer
 publish_year | integer
 name | character
 isbn | text
 author | character
 publisher | character


Table: course
 faculty | integer
 id | integer
 category | integer
 name | character
 course_describtion | text


Table: gorup_discuss_rating
 id | integer
 group_discuss | integer
 student | integer
 rating | integer
 timestamp | timestamp without time zone


