mermaid-erd Skill | Agent Skills

Analyze SQL schema files and generate a Mermaid entity relationship diagram.

Arguments: Path to SQL file(s) or directory containing schema files (*.sql)

Steps:

Find and read all relevant SQL schema files
Parse each table definition extracting:
- Table name
- Columns with types
- Primary keys (PK)
- Foreign keys (FK) and their references
- Unique constraints (UK)
Generate a Mermaid erDiagram showing:
- Each table as an entity with its columns
- Relationships based on foreign keys
- Cardinality notation (one-to-one, one-to-many, many-to-many)
Validate diagram by running: npx -y @mermaid-js/mermaid-cli mmdc -i /dev/stdin -o /dev/null <<< '<diagram>'
- If validation fails, fix syntax errors and retry
Verify complete coverage:
- List any tables not included in the diagram
- List any foreign key relationships not represented

Output format:

erDiagram
    users {
        int id PK
        string email UK
        string name
        timestamp created_at
    }

    posts {
        int id PK
        int user_id FK
        string title
        text content
    }

    users ||--o{ posts : "has many"

Relationship notation:

||--|| one-to-one
||--o{ one-to-many
o{--o{ many-to-many (via junction table)

Notes:

Simplify SQL types to readable names (VARCHAR -> string, INTEGER -> int, etc.)
Include PK/FK/UK markers on relevant columns
Name relationships descriptively when possible
For large schemas, consider grouping related tables or generating multiple diagrams

Agent Skills: mermaid-erd

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