---
title: "Schema Visualization"
description: "Schema Visualization"
type: "docs"
category: "doc"
tags: []
authors: [Anonymous]
date: "2026-09-09"
last_update: "2026-09-09"
time_minutes: 4
draft: false
unlisted: false
url: "https://www.derafu.dev/docs/data/etl/schema-visualization"
---

# Schema Visualization

Derafu ETL includes powerful tools for visualizing database schemas through various output formats. These visualizations are useful for documentation, planning, and understanding the structure of your data.

## Available Visualization Formats

Derafu ETL supports multiple visualization formats through schema targets:

- **Markdown**: Human-readable documentation.
- **D2**: Interactive entity-relationship diagrams.
- **Text**: Simple text representation.
- **SQL**: Database creation scripts.
- **Doctrine Schema**: Programmatic schema representation.

## Using Schema Targets

Schema targets implement the `SchemaTargetInterface` and convert a schema to a specific format.

### Basic Usage

All schema targets follow a similar pattern:

```php
use Derafu\ETL\Database\DatabaseManager;
use Derafu\ETL\Schema\Target\CustomSchemaTarget; // Just an example.

// Connect to the database.
$manager = new DatabaseManager();
$database = $manager->connect('database.sqlite');

// Get the schema.
$schema = $database->schema();

// Create the target.
$target = new CustomSchemaTarget();

// Apply the schema to the target.
$output = $target->applySchema($schema);

// Use the output.
file_put_contents('output-file.custom', $output);
```

## Markdown Schema

The `MarkdownSchemaTarget` generates comprehensive Markdown documentation for your database schema.

```php
use Derafu\ETL\Schema\Target\MarkdownSchemaTarget;

$target = new MarkdownSchemaTarget();
$markdown = $target->applySchema($schema);

file_put_contents('schema.md', $markdown);
```

The generated Markdown includes:

- Table of contents.
- Detailed table definitions.
- Column information with types and constraints.
- Primary keys, indexes, and foreign key relationships.

Example output:

```markdown
# Database Schema

## Table of Contents

- [Table: users](#table-users)
- [Table: posts](#table-posts)

## Table: users {#table-users}

### Columns

| Column     | Type        | Attributes              | Description |
|------------|-------------|-------------------------|-------------|
| id         | integer     | PRIMARY KEY / NOT NULL  |             |
| username   | string(100) | NOT NULL                |             |
| email      | string(255) | NOT NULL                |             |
| created_at | datetime    | NOT NULL                |             |

### Primary Key

- Columns: `id`

### Indexes

| Name         | Columns  | Type   | Flags |
|--------------|----------|--------|-------|
| idx_username | username | INDEX  |       |
| idx_email    | email    | UNIQUE |       |
```

## D2 Diagrams

The `D2SchemaTarget` generates diagrams in [D2 format](https://d2lang.com/), a modern diagram scripting language.

```php
use Derafu\ETL\Schema\Target\D2SchemaTarget;

$target = new D2SchemaTarget(
    detailLevel: D2SchemaTarget::DETAIL_FULL,
    direction: D2SchemaTarget::DIRECTION_RIGHT,
    layout: D2SchemaTarget::LAYOUT_DEFAULT,
    includeIndexes: true
);
$d2 = $target->applySchema($schema);

file_put_contents('schema.d2', $d2);
```

Options include:

- **Detail Level**: `DETAIL_FULL`, `DETAIL_KEYS_ONLY`, `DETAIL_MINIMAL`.
- **Direction**: `DIRECTION_UP`, `DIRECTION_DOWN`, `DIRECTION_LEFT`, `DIRECTION_RIGHT`.
- **Layout**: `LAYOUT_DEFAULT`, `LAYOUT_CLUSTERED`, `LAYOUT_HIERARCHICAL`.
- **Include Indexes**: Whether to include indexes in the diagram.

Example D2 output:

```
# Database Schema

direction: right

# Tables
users: {
  shape: sql_table
  id: integer NOT NULL pk
  username: string(100) NOT NULL column
  email: string(255) NOT NULL column
  created_at: datetime NOT NULL column
}

posts: {
  shape: sql_table
  id: integer NOT NULL pk
  user_id: integer NOT NULL fk
  title: string(255) NOT NULL column
  content: text column
  created_at: datetime NOT NULL column
}

# Relationships
posts -> users
```

## Practical Applications

### Documentation

Generate comprehensive documentation for your database:

```php
use Derafu\ETL\Database\DatabaseManager;
use Derafu\ETL\Schema\Target\MarkdownSchemaTarget;

$manager = new DatabaseManager();
$database = $manager->connect('production.sqlite');

$target = new MarkdownSchemaTarget();
$docs = $target->applySchema($database->schema());

file_put_contents('database-schema.md', $docs);
```

### Visual Modeling

Create visual diagrams for presentations or analysis:

```php
use Derafu\ETL\Schema\Target\D2SchemaTarget;

// Filter to only show specific tables.
$target = new D2SchemaTarget(
    tableFilter: ['users', 'posts', 'comments']
);

$diagram = $target->applySchema($schema);
file_put_contents('entity-relationship.d2', $diagram);
```

### Schema Migration

Export a schema definition to create a new database:

```php
use Derafu\ETL\Schema\Target\SqliteSchemaTarget;

$target = new SqliteSchemaTarget();
$sql = $target->applySchema($schema);

file_put_contents('schema.sql', $sql);
```

## Integration with ETL Pipeline

Schema visualization can be integrated with the ETL pipeline for comprehensive documentation:

```php
use Derafu\ETL\Pipeline\Pipeline;
use Derafu\ETL\Schema\Target\MarkdownSchemaTarget;

// Run ETL pipeline.
$pipeline = new Pipeline();
$result = $pipeline
    ->extract('data.xlsx')
    ->transform()
    ->load('database.sqlite')
    ->execute();

// Document the resulting database.
$database = $result->target()->database();
$target = new MarkdownSchemaTarget();
$docs = $target->applySchema($database->schema());

file_put_contents('database-schema.md', $docs);
```



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Last updated on 09/09/2026