313 lines
6.6 KiB
Markdown
313 lines
6.6 KiB
Markdown
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# Database Schema (ERD) Documentation
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## 📊 Entity-Relationship Diagram
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### Online Visualization
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View the interactive ERD diagram:
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- **dbdiagram.io**: [dbdiagram.io](https://dbdiagram.io/d/e-lerning-6943c64be4bb1dd3a9896479)
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## 📋 Database Overview
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### Total Tables: **17**
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| Category | Tables | Count |
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|----------|--------|-------|
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| **Core** | users, categories, courses, chapters, lessons | 5 |
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| **Content** | quizzes, questions, choices, lesson_attachments | 4 |
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| **Progress** | enrollments, lesson_progress, quiz_attempts | 3 |
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| **Communication** | announcements, announcement_attachments | 2 |
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| **Commerce** (อนาคต) | orders, payments, withdrawals | 3 |
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---
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## 🎯 Key Features
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### 1. **Multi-language Support**
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- Uses `jsonb` fields for Thai/English content
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- Fields: `title`, `content`, `description`
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### 2. **Video Progress Tracking**
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- Track playback position per student
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- Auto-complete at 90% watched
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- Resume from last position
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### 3. **Lesson Prerequisites**
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- Sequential learning control
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- Quiz pass requirements
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- Flexible ordering
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### 4. **File Attachments**
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- Multiple files per lesson
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- Support for PDF, DOCX, ZIP, images
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- Sortable with descriptions
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### 5. **Quiz System**
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- Multiple attempts with cooldown
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- Score policies (HIGHEST/LATEST/FIRST/AVERAGE)
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- Detailed attempt history
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---
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## 📊 Main Entities
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### Users
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- Roles: STUDENT, INSTRUCTOR, ADMIN
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- Profile information
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- Authentication data
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### Courses
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- Multi-language titles and descriptions
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- Categories and pricing
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- Instructor ownership
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- Approval workflow
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### Chapters & Lessons
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- Hierarchical structure
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- Sort ordering
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- Multiple lesson types (video, pdf, text, quiz)
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- Prerequisites support
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### Progress Tracking
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- Enrollment status
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- Lesson completion
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- Video playback position
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- Quiz attempts and scores
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---
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## 🔗 Relationships
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```
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users (1) ──── (many) courses [instructor]
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users (1) ──── (many) enrollments
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users (1) ──── (many) lesson_progress
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users (1) ──── (many) quiz_attempts
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courses (1) ──── (many) chapters
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courses (1) ──── (many) enrollments
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courses (1) ──── (many) announcements
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chapters (1) ──── (many) lessons
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lessons (1) ──── (many) lesson_attachments
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lessons (1) ──── (many) lesson_progress
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lessons (1) ──── (many) quizzes
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quizzes (1) ──── (many) questions
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quizzes (1) ──── (many) quiz_attempts
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questions (1) ──── (many) choices
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```
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---
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## 🎨 How to Visualize
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### Using dbdiagram.io
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1. **Open dbdiagram.io**
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- Go to [https://dbdiagram.io/d](https://dbdiagram.io/d)
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2. **Import Schema**
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- Click "Import" button (top right)
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- Select "From DBML"
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- Copy contents from [`ERD_v2_improved.txt`](./ERD_v2_improved.txt)
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- Paste into the editor
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- Click "Import"
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3. **View Diagram**
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- Zoom in/out with mouse wheel
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- Drag to pan
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- Click tables to highlight relationships
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- Export as PNG/PDF/SQL
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### Alternative Tools
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- **DBeaver**: Import SQL and generate ER diagram
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- **MySQL Workbench**: Reverse engineer from database
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- **pgAdmin**: PostgreSQL schema visualization
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- **draw.io**: Manual diagram creation
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---
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## 📝 Table Descriptions
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### Core Tables
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#### `users`
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- User accounts and authentication
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- Roles: STUDENT, INSTRUCTOR, ADMIN
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- Profile information
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#### `categories`
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- Course categorization
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- Multi-language names
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#### `courses`
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- Course information and metadata
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- Pricing and approval status
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- Instructor ownership
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#### `chapters`
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- Course structure organization
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- Sortable within courses
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#### `lessons`
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- Learning content units
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- Types: video, pdf, text, quiz
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- Prerequisites and sequencing
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### Content Tables
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#### `quizzes`
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- Assessment configuration
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- Attempt limits and cooldown
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- Passing score requirements
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#### `questions`
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- Quiz questions
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- Types: multiple_choice, true_false
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- Point values
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#### `choices`
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- Answer options for questions
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- Correct answer marking
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#### `lesson_attachments`
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- Supplementary files
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- PDFs, documents, code samples
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- Multi-language descriptions
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### Progress Tables
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#### `enrollments`
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- Student course registrations
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- Progress tracking
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- Certificate issuance
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#### `lesson_progress`
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- Lesson completion status
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- Video playback position
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- Watch history
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#### `quiz_attempts`
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- Quiz submission records
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- Scores and answers
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- Attempt history
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### Communication Tables
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#### `announcements`
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- Course announcements
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- Pinning and scheduling
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- Multi-language content
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#### `announcement_attachments`
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- Announcement file attachments
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---
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## 🔧 Database Constraints
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### Primary Keys
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- All tables use auto-incrementing integer PKs
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### Foreign Keys
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- Maintain referential integrity
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- Cascade deletes where appropriate
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### Unique Constraints
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- `(user_id, course_id)` in enrollments
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- `(user_id, lesson_id)` in lesson_progress
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- Email in users
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### Check Constraints (via notes)
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- Progress percentages: 0-100
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- Scores: 0-100
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- Sort orders: >= 0
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- Prices: >= 0
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### Indexes
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- Single column indexes on FKs
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- Composite indexes for common queries
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- JSONB GIN indexes for multi-language fields
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---
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## 🚀 Migration Notes
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### PostgreSQL Extensions Required
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```sql
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CREATE EXTENSION IF NOT EXISTS "uuid-ossp";
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CREATE EXTENSION IF NOT EXISTS "pg_trgm"; -- for text search
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```
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### JSONB Usage
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```sql
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-- Multi-language fields
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title JSONB -- {"th": "...", "en": "..."}
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-- Query examples
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WHERE title->>'th' LIKE '%Python%'
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WHERE title @> '{"en": "Introduction"}'
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```
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### Soft Delete Pattern
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```sql
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-- Recommended for important tables
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ALTER TABLE courses ADD COLUMN deleted_at TIMESTAMP;
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CREATE INDEX idx_courses_deleted ON courses(deleted_at) WHERE deleted_at IS NULL;
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```
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---
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## 📈 Performance Considerations
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### Indexes Created
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- All foreign keys
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- Composite indexes for (course_id, sort_order)
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- User email for login
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- Course status for filtering
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- Last watched timestamp for recent videos
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### Query Optimization
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- Use `SELECT` specific columns
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- Implement pagination
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- Cache course lists in Redis
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- Use database views for complex queries
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---
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## 🔗 Related Documentation
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- [API Endpoints](./api_endpoints.md) - REST API reference
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- [Edge Cases](../edge_cases_quick_reference.md) - Special scenarios
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- [Development Setup](../development_setup.md) - Environment configuration
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---
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## 📊 Statistics
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- **Total Tables**: 17
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- **Total Relationships**: 20+
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- **Multi-language Fields**: 15+
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- **Indexed Columns**: 40+
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- **JSONB Fields**: 15+
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---
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## 🎯 Next Steps
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1. ✅ Review ERD schema
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2. ⏳ Create PostgreSQL database
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3. ⏳ Run migrations
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4. ⏳ Seed initial data
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5. ⏳ Implement API endpoints
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6. ⏳ Test with sample data
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---
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**Last Updated**: 2024-12-24
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**Version**: 2.0 (Improved)
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