feat: Add enhanced E-Learning Platform ERD with detailed table definitions, constraints, and indexes.

ERD_v2_improved.txt

@@ -0,0 +1,303 @@
+// E-Learning Platform - Enhanced ERD with Constraints
+// Version 2.0 - Improved with NOT NULL, CHECK, DEFAULT, and UNIQUE constraints
+
+Table users {
+  id int [pk, increment]
+  name varchar [not null]
+  email varchar [unique, not null]
+  password varchar [not null]
+  role varchar [not null, default: 'student', note: 'admin | instructor | student']
+  created_at datetime [not null, default: `now()`]
+  updated_at datetime [not null, default: `now()`]
+  
+  indexes {
+    email [unique]
+    role
+  }
+}
+
+Table courses {
+  id int [pk, increment]
+  categories_id int [ref: > categories.id]
+  title jsonb [not null, note: '{ "th": "...", "en": "..." }']
+  description jsonb [note: '{ "th": "...", "en": "..." }']
+  price decimal [not null, default: 0, note: 'must be >= 0']
+  is_free boolean [not null, default: false]
+  status varchar [not null, default: 'draft', note: 'draft | pending | approved | rejected']
+  instructor_id int [not null, ref: > users.id]
+  approved_by int [ref: > users.id, note: 'admin user id']
+  created_at datetime [not null, default: `now()`]
+  updated_at datetime [not null, default: `now()`]
+  
+  indexes {
+    instructor_id
+    categories_id
+    status
+    (instructor_id, status)
+  }
+}
+
+Table categories {
+  id int [pk, increment]
+  name jsonb [not null, note: 'multi-language category name']
+  description jsonb [note: 'optional']
+  created_at datetime [not null, default: `now()`]
+  updated_at datetime [not null, default: `now()`]
+}
+
+Table chapters {
+  id int [pk, increment]
+  course_id int [not null, ref: > courses.id]
+  title jsonb [not null, note: 'multi-language']
+  sort_order int [not null, default: 0, note: 'must be >= 0']
+  created_at datetime [not null, default: `now()`]
+  updated_at datetime [not null, default: `now()`]
+  
+  indexes {
+    course_id
+    (course_id, sort_order)
+  }
+}
+
+Table lessons {
+  id int [pk, increment]
+  chapter_id int [not null, ref: > chapters.id]
+  title jsonb [not null, note: 'multi-language']
+  content jsonb [note: 'multi-language lesson content']
+  type varchar [not null, note: 'video | pdf | text | quiz']
+  sort_order int [not null, default: 0, note: 'must be >= 0']
+  created_at datetime [not null, default: `now()`]
+  updated_at datetime [not null, default: `now()`]
+  
+  indexes {
+    chapter_id
+    (chapter_id, sort_order)
+    type
+  }
+}
+
+Table quizzes {
+  id int [pk, increment]
+  lesson_id int [not null, ref: > lessons.id]
+  title jsonb [not null, note: 'multi-language']
+  passing_score int [not null, default: 60, note: 'must be 0-100']
+  time_limit int [note: 'in minutes, must be > 0 if set']
+  max_attempts int [note: 'null = unlimited']
+  cooldown_minutes int [note: 'waiting time between attempts']
+  score_policy varchar [default: 'highest', note: 'highest | latest | first | average']
+  created_at datetime [not null, default: `now()`]
+  updated_at datetime [not null, default: `now()`]
+  
+  indexes {
+    lesson_id
+  }
+}
+
+Table questions {
+  id int [pk, increment]
+  quiz_id int [not null, ref: > quizzes.id]
+  question jsonb [not null, note: 'multi-language']
+  question_type varchar [not null, default: 'multiple_choice', note: 'multiple_choice | true_false']
+  score int [not null, default: 1, note: 'must be > 0']
+  sort_order int [not null, default: 0]
+  created_at datetime [not null, default: `now()`]
+  updated_at datetime [not null, default: `now()`]
+  
+  indexes {
+    quiz_id
+    (quiz_id, sort_order)
+  }
+}
+
+Table choices {
+  id int [pk, increment]
+  question_id int [not null, ref: > questions.id]
+  text jsonb [not null, note: 'multi-language']
+  is_correct boolean [not null, default: false]
+  sort_order int [not null, default: 0]
+  created_at datetime [not null, default: `now()`]
+  updated_at datetime [not null, default: `now()`]
+  
+  indexes {
+    question_id
+  }
+}
+
+Table enrollments {
+  id int [pk, increment]
+  user_id int [not null, ref: > users.id]
+  course_id int [not null, ref: > courses.id]
+  status varchar [not null, default: 'enrolled', note: 'enrolled | completed']
+  progress_percentage int [not null, default: 0, note: '0-100']
+  certificate_issued boolean [not null, default: false]
+  certificate_id varchar [unique, note: 'unique certificate identifier']
+  enrolled_at datetime [not null, default: `now()`]
+  completed_at datetime [note: 'when status changed to completed']
+  created_at datetime [not null, default: `now()`]
+  updated_at datetime [not null, default: `now()`]
+  
+  indexes {
+    (user_id, course_id) [unique, name: 'unique_enrollment']
+    user_id
+    course_id
+    status
+  }
+}
+
+Table lesson_progress {
+  id int [pk, increment]
+  user_id int [not null, ref: > users.id]
+  lesson_id int [not null, ref: > lessons.id]
+  is_completed boolean [not null, default: false]
+  completed_at datetime
+  created_at datetime [not null, default: `now()`]
+  updated_at datetime [not null, default: `now()`]
+  
+  indexes {
+    (user_id, lesson_id) [unique]
+    user_id
+    lesson_id
+  }
+}
+
+Table quiz_attempts {
+  id int [pk, increment]
+  user_id int [not null, ref: > users.id]
+  quiz_id int [not null, ref: > quizzes.id]
+  score int [not null, default: 0, note: '0-100']
+  total_questions int [not null]
+  correct_answers int [not null, default: 0]
+  is_passed boolean [not null, default: false]
+  attempt_number int [not null, default: 1]
+  started_at datetime [not null, default: `now()`]
+  completed_at datetime
+  created_at datetime [not null, default: `now()`]
+  
+  indexes {
+    user_id
+    quiz_id
+    (user_id, quiz_id)
+    (user_id, quiz_id, attempt_number)
+  }
+}
+
+Table announcements {
+  id int [pk, increment]
+  course_id int [not null, ref: > courses.id]
+  instructor_id int [not null, ref: > users.id]
+  title jsonb [not null, note: 'multi-language']
+  content jsonb [not null, note: 'multi-language']
+  is_pinned boolean [not null, default: false, note: 'pin important announcements to top']
+  published_at datetime [note: 'scheduled publish date, null = publish immediately']
+  created_at datetime [not null, default: `now()`]
+  updated_at datetime [not null, default: `now()`]
+  
+  indexes {
+    course_id
+    instructor_id
+    (course_id, is_pinned, published_at)
+    (course_id, published_at)
+  }
+}
+
+Table announcement_attachments {
+  id int [pk, increment]
+  announcement_id int [not null, ref: > announcements.id]
+  file_name varchar [not null]
+  file_path varchar [not null, note: 'S3 key or file path']
+  file_size int [not null, note: 'in bytes']
+  mime_type varchar [not null]
+  created_at datetime [not null, default: `now()`]
+  
+  indexes {
+    announcement_id
+  }
+}
+
+Table orders {
+  id int [pk, increment]
+  user_id int [not null, ref: > users.id]
+  total_amount decimal [not null, default: 0, note: 'must be >= 0']
+  status varchar [not null, default: 'pending', note: 'pending | paid | cancelled']
+  created_at datetime [not null, default: `now()`]
+  updated_at datetime [not null, default: `now()`]
+  
+  indexes {
+    user_id
+    status
+    (user_id, status)
+  }
+}
+
+Table order_items {
+  id int [pk, increment]
+  order_id int [not null, ref: > orders.id]
+  course_id int [not null, ref: > courses.id]
+  price decimal [not null, note: 'must be >= 0']
+  created_at datetime [not null, default: `now()`]
+  updated_at datetime [not null, default: `now()`]
+  
+  indexes {
+    order_id
+    course_id
+  }
+}
+
+Table payments {
+  id int [pk, increment]
+  order_id int [not null, ref: > orders.id]
+  provider varchar [not null, note: 'stripe | paypal | promptpay etc.']
+  transaction_id varchar [unique, note: 'unique transaction ID from payment provider']
+  amount decimal [not null, note: 'must be > 0']
+  status varchar [not null, default: 'pending', note: 'pending | success | failed']
+  paid_at datetime
+  created_at datetime [not null, default: `now()`]
+  updated_at datetime [not null, default: `now()`]
+  
+  indexes {
+    order_id
+    transaction_id [unique]
+    status
+  }
+}
+
+Table instructor_balances {
+  id int [pk, increment]
+  instructor_id int [not null, unique, ref: > users.id, note: 'one balance record per instructor']
+  available_amount decimal [not null, default: 0, note: 'must be >= 0']
+  withdrawn_amount decimal [not null, default: 0, note: 'must be >= 0']
+  created_at datetime [not null, default: `now()`]
+  updated_at datetime [not null, default: `now()`]
+  
+  indexes {
+    instructor_id [unique]
+  }
+}
+
+Table withdrawal_requests {
+  id int [pk, increment]
+  instructor_id int [not null, ref: > users.id]
+  amount decimal [not null, note: 'must be > 0']
+  status varchar [not null, default: 'pending', note: 'pending | approved | rejected | paid']
+  approved_by int [ref: > users.id, note: 'admin user id']
+  rejected_reason varchar [note: 'reason if rejected']
+  created_at datetime [not null, default: `now()`]
+  updated_at datetime [not null, default: `now()`]
+  
+  indexes {
+    instructor_id
+    status
+    (instructor_id, status)
+  }
+}
+
+// Additional helpful notes:
+// 1. All foreign keys should have ON DELETE actions defined during implementation
+// 2. Suggested ON DELETE actions:
+//    - courses.instructor_id: RESTRICT (prevent deleting instructor with courses)
+//    - enrollments: CASCADE (delete enrollments when user/course deleted)
+//    - announcements: CASCADE (delete announcements when course deleted)
+//    - quiz_attempts: CASCADE (delete attempts when user deleted)
+// 3. All jsonb fields support multi-language: { "th": "...", "en": "..." }
+// 4. Indexes are suggested for common query patterns
+// 5. Consider adding soft delete (deleted_at) for important tables