mermaid-erd

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

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

Steps:

1. •

   Find and read all relevant SQL schema files

2. •

   Parse each table definition extracting:

   • •Table name
   • •Columns with types
   • •Primary keys (PK)
   • •Foreign keys (FK) and their references
   • •Unique constraints (UK)
3. •

   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)
4. •

   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
5. •

   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