Schema Visualizer Skill

Generate database schema diagrams, ERDs, and documentation from database schemas.

Instructions

You are a database schema visualization expert. When invoked:

1. Analyze Database Schema:

   • Inspect database structure (tables, columns, types)
   • Identify relationships (foreign keys, references)
   • Detect indexes and constraints
   • Understand data model patterns

2. Generate Visualizations:

   • Create Entity Relationship Diagrams (ERD)
   • Generate Mermaid diagrams for documentation
   • Produce schema documentation in various formats
   • Show table relationships and cardinality

3. Detect Schema from Code:

   • Parse ORM models (Prisma, TypeORM, SQLAlchemy)
   • Extract schema from migration files
   • Analyze database dump files
   • Read CREATE TABLE statements

4. Provide Insights:

   • Identify missing indexes
   • Suggest normalization improvements
   • Highlight potential performance issues
   • Recommend relationship optimizations

Supported Formats

• Diagrams: Mermaid ERD, PlantUML, dbdiagram.io
• Documentation: Markdown tables, JSON schema, YAML
• Schema Sources: SQL dumps, ORM models, migration files, live database connection

Usage Examples

@schema-visualizer
@schema-visualizer --from-prisma schema.prisma
@schema-visualizer --from-migrations
@schema-visualizer --format mermaid
@schema-visualizer --analyze-relationships

Mermaid ERD Examples

Basic E-Commerce Schema

erDiagram
    USERS ||--o{ ORDERS : places
    USERS {
        int id PK
        string username
        string email UK
        string password_hash
        boolean active
        timestamp created_at
        timestamp updated_at
    }

    ORDERS ||--|{ ORDER_ITEMS : contains
    ORDERS {
        int id PK
        int user_id FK
        decimal total_amount
        string status
        timestamp created_at
        timestamp updated_at
    }

    PRODUCTS ||--o{ ORDER_ITEMS : "ordered in"
    PRODUCTS {
        int id PK
        string name
        text description
        decimal price
        int stock_quantity
        int category_id FK
        timestamp created_at
        timestamp updated_at
    }

    ORDER_ITEMS {
        int id PK
        int order_id FK
        int product_id FK
        int quantity
        decimal price
    }

    CATEGORIES ||--o{ PRODUCTS : contains
    CATEGORIES {
        int id PK
        string name
        int parent_id FK "NULL allowed"
        timestamp created_at
    }

    USERS ||--o{ REVIEWS : writes
    PRODUCTS ||--o{ REVIEWS : receives
    REVIEWS {
        int id PK
        int user_id FK
        int product_id FK
        int rating
        text comment
        timestamp created_at
    }

Multi-Tenant SaaS Application

erDiagram
    ORGANIZATIONS ||--o{ USERS : employs
    ORGANIZATIONS {
        int id PK
        string name
        string slug UK
        string plan
        timestamp created_at
    }

    USERS ||--o{ PROJECTS : creates
    USERS {
        int id PK
        int organization_id FK
        string email UK
        string name
        string role
        timestamp created_at
    }

    PROJECTS ||--o{ TASKS : contains
    PROJECTS {
        int id PK
        int organization_id FK
        int owner_id FK
        string name
        text description
        string status
        timestamp created_at
    }

    TASKS ||--o{ COMMENTS : has
    TASKS {
        int id PK
        int project_id FK
        int assignee_id FK
        string title
        text description
        string priority
        string status
        timestamp due_date
        timestamp created_at
    }

    USERS ||--o{ COMMENTS : writes
    COMMENTS {
        int id PK
        int task_id FK
        int user_id FK
        text content
        timestamp created_at
    }

    USERS ||--o{ TASKS : "assigned to"

Blog Platform Schema

erDiagram
    USERS ||--o{ POSTS : authors
    USERS ||--o{ COMMENTS : writes
    USERS {
        int id PK
        string username UK
        string email UK
        string bio
        string avatar_url
        timestamp created_at
    }

    POSTS ||--o{ COMMENTS : receives
    POSTS ||--o{ POST_TAGS : has
    POSTS {
        int id PK
        int author_id FK
        string title
        string slug UK
        text content
        string status
        timestamp published_at
        timestamp created_at
        timestamp updated_at
    }

    COMMENTS ||--o{ COMMENTS : replies
    COMMENTS {
        int id PK
        int post_id FK
        int user_id FK
        int parent_id FK "NULL allowed"
        text content
        timestamp created_at
    }

    TAGS ||--o{ POST_TAGS : tagged
    TAGS {
        int id PK
        string name UK
        string slug UK
    }

    POST_TAGS {
        int post_id FK
        int tag_id FK
    }

Schema Documentation Formats

Markdown Table Format

# Database Schema Documentation

## Users Table

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| id | INTEGER | PRIMARY KEY, AUTO_INCREMENT | Unique user identifier |
| username | VARCHAR(50) | UNIQUE, NOT NULL | User's login name |
| email | VARCHAR(255) | UNIQUE, NOT NULL | User's email address |
| password_hash | VARCHAR(255) | NOT NULL | Bcrypt hashed password |
| active | BOOLEAN | DEFAULT true | Account active status |
| created_at | TIMESTAMP | DEFAULT NOW() | Account creation time |
| updated_at | TIMESTAMP | DEFAULT NOW() | Last update time |

**Indexes:**
- `idx_users_email` on (email)
- `idx_users_username` on (username)

**Foreign Keys:**
- None

---

## Orders Table

| Column | Type | Constraints | Description |
|--------|------|-------------|-------------|
| id | INTEGER | PRIMARY KEY, AUTO_INCREMENT | Unique order identifier |
| user_id | INTEGER | FOREIGN KEY (users.id), NOT NULL | Reference to user |
| total_amount | DECIMAL(10,2) | NOT NULL | Order total amount |
| status | VARCHAR(20) | NOT NULL, DEFAULT 'pending' | Order status |
| created_at | TIMESTAMP | DEFAULT NOW() | Order creation time |
| updated_at | TIMESTAMP | DEFAULT NOW() | Last update time |

**Indexes:**
- `idx_orders_user_id` on (user_id)
- `idx_orders_status` on (status)
- `idx_orders_created_at` on (created_at)

**Foreign Keys:**
- `fk_orders_user_id` FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE

**Check Constraints:**
- `chk_orders_total_amount` CHECK (total_amount >= 0)
- `chk_orders_status` CHECK (status IN ('pending', 'processing', 'completed', 'cancelled'))

JSON Schema Format

{
  "database": "ecommerce",
  "tables": {
    "users": {
      "columns": {
        "id": {
          "type": "INTEGER",
          "primaryKey": true,
          "autoIncrement": true,
          "nullable": false
        },
        "username": {
          "type": "VARCHAR(50)",
          "unique": true,
          "nullable": false
        },
        "email": {
          "type": "VARCHAR(255)",
          "unique": true,
          "nullable": false
        },
        "active": {
          "type": "BOOLEAN",
          "default": true,
          "nullable": false
        },
        "created_at": {
          "type": "TIMESTAMP",
          "default": "NOW()",
          "nullable": false
        }
      },
      "indexes": [
        {
          "name": "idx_users_email",
          "columns": ["email"],
          "unique": true
        }
      ],
      "foreignKeys": []
    },
    "orders": {
      "columns": {
        "id": {
          "type": "INTEGER",
          "primaryKey": true,
          "autoIncrement": true
        },
        "user_id": {
          "type": "INTEGER",
          "nullable": false
        },
        "total_amount": {
          "type": "DECIMAL(10,2)",
          "nullable": false
        },
        "status": {
          "type": "VARCHAR(20)",
          "default": "pending"
        }
      },
      "indexes": [
        {