erdDiagram

Command: erdDiagram
Category: Analysis Tools
Status: Early Access

Description

Generate Entity Relationship (ER) diagrams from your database schema. ER diagrams provide a visual representation of your data structure, showing how tables relate to each other and what data they contain.

What is an ER Diagram (ERD)?

An Entity Relationship Diagram (ERD) is a visual representation of database structure that shows:

• Entities: Tables/objects in the database, drawn as rectangles
• Attributes: Columns/fields within each entity
• Relationships: Connections between entities showing how they relate
• Cardinality: The nature of relationships (one-to-one, one-to-many, many-to-many)

Example structure:

CUSTOMERS ──────┐ (one customer)
                │ can place many
                ├─── ORDERS ──────┐ (one order)
                │                 │ contains many
                │                 └─── ORDER_ITEMS ──── PRODUCTS
                │
            Places          Contains

What Do You Use ERD Diagrams For?

1. System Understanding & Documentation

• Visualize the complete database structure at a glance
• Communicate data model to team members and stakeholders
• Create documentation for new developers joining the project
• Maintain up-to-date architecture diagrams as schemas evolve

2. Database Design & Planning

• Plan new database schemas before implementation
• Validate relationships between entities
• Identify missing relationships or anomalies
• Ensure proper normalization and structure
• Design views for common data combinations

3. Application Development

• Helps developers understand data structure when writing queries
• Clarifies which tables to join for specific data requirements
• Identifies potential performance issues (too many joins)
• Guides ORM model design (Entity Framework, Hibernate, etc.)
• Prevents mistakes in query development

4. Data Migration & Integration

• Map source and target schemas during data migration
• Identify equivalent tables and fields when integrating systems
• Validate data transformation logic
• Plan extraction queries for ETL processes
• Compare schemas between environments (dev, test, prod)

5. Performance & Optimization

• Identifies tables with many relationships (potential bottlenecks)
• Helps spot unnecessary complexity in data model
• Reveals missing denormalization opportunities
• Shows which tables are joined frequently (candidates for indexing)
• Guides partitioning strategy for large tables

6. Data Governance & Quality

• Documents data lineage and relationships
• Identifies critical data dependencies
• Shows impact analysis when modifying schemas
• Helps implement data quality rules
• Supports compliance documentation requirements

7. Troubleshooting & Analysis

• Quickly understand relationships when investigating data issues
• Trace problems through related tables
• Identify data consistency violations
• Review foreign key constraints
• Debug query performance issues by visualizing join paths

Key Components in an ERD

Entities - Represent tables:

┌──────────────┐
│   CUSTOMERS  │
├──────────────┤
│ CUSTOMER_ID  │
│ NAME         │
│ EMAIL        │
└──────────────┘

Relationships - Show how entities connect:

• 1:1 - One-to-one relationship
• 1:N - One-to-many relationship (most common)
• M:N - Many-to-many relationship

Cardinality Notation:

• || - One (mandatory)
• o| - Zero or one
• || - Many
• |o - Zero or many

Common Use Cases

Scenario 1: New Developer Onboarding

# Generate a diagram for new developer to understand the schema
hana-cli erdDiagram --schema SALES --format mermaid --output sales-schema.md

Scenario 2: Migration Planning

# Export current schema structure as reference
hana-cli erdDiagram --schema LEGACY_SYSTEM --output legacy-schema.json --format json

Scenario 3: Documentation Update

# Generate PlantUML diagram for inclusion in architecture docs
hana-cli erdDiagram --schema PRODUCTION --showColumns --format plantuml --output arch-diagram.puml

Scenario 4: Specific Subsystem

# Diagram only billing-related tables
hana-cli erdDiagram -s ACCOUNTING -t INVOICES,INVOICE_ITEMS,CUSTOMERS,PAYMENTS

Syntax

hana-cli erdDiagram [options]

Aliases

• erd
• er
• schema-diagram
• entityrelation

Command Diagram

Parameters

Positional Arguments

This command has no positional arguments.

Options

Option	Alias	Type	Default	Description
--schema	-s	string	CURRENT_SCHEMA	Schema to diagram
--tables	-t	string	optional	Comma-separated list of tables (empty for all)
--output	-o	string	optional	Output file for diagram
--format	-f	string	mermaid	Diagram format (mermaid, plantuml, graphviz, json)
--showCardinality	-c	boolean	true	Show relationship cardinality
--showColumns	--cols	boolean	true	Show table columns in diagram
--excludeColumns	--ec	string	optional	Comma-separated columns to exclude
--profile	-p	string	optional	CDS Profile
--help	-h	boolean	-	Show help message

Connection Parameters

Option	Alias	Type	Default	Description
--admin	-a	boolean	false	Connect via admin (default-env-admin.json)
--conn	-	string	-	Connection filename to override default-env.json

Troubleshooting

Option	Alias	Type	Default	Description
--disableVerbose	--quiet	boolean	false	Disable verbose output - removes extra output mainly intended for human-readable usage
--debug	-d	boolean	false	Debug hana-cli itself by adding lots of intermediate details

For a complete list of parameters and options, use:

hana-cli erdDiagram --help

Output Formats

Mermaid Format (Default)

Generates a Mermaid ER diagram in markdown format:

PlantUML Format

Generates PlantUML diagram code:

@startuml
entity CUSTOMERS {
    * CUSTOMER_ID : int <<generated>>
    --
    NAME : string
    EMAIL : string
    PHONE : string
}

entity ORDERS {
    * ORDER_ID : int <<generated>>
    --
    CUSTOMER_ID : int <<FK>>
    ORDER_DATE : date
    TOTAL_AMOUNT : decimal
}

entity ORDER_ITEMS {
    * ORDER_ITEM_ID : int <<generated>>
    --
    ORDER_ID : int <<FK>>
    PRODUCT_ID : int <<FK>>
    QUANTITY : int
    UNIT_PRICE : decimal
}

CUSTOMERS ||--o{ ORDERS : places
ORDERS ||--|{ ORDER_ITEMS : contains
@enduml

GraphViz Format

Generates GraphViz DOT format for visualization:

digraph schema {
    rankdir=LR;
    
    CUSTOMERS [label="CUSTOMERS|CUSTOMER_ID|NAME|EMAIL|PHONE"];
    ORDERS [label="ORDERS|ORDER_ID|CUSTOMER_ID|ORDER_DATE|TOTAL_AMOUNT"];
    ORDER_ITEMS [label="ORDER_ITEMS|ORDER_ITEM_ID|ORDER_ID|PRODUCT_ID|QUANTITY|UNIT_PRICE"];
    PRODUCTS [label="PRODUCTS|PRODUCT_ID|PRODUCT_NAME|PRICE|STOCK_QUANTITY"];
    
    CUSTOMERS -> ORDERS [label="1..n"];
    ORDERS -> ORDER_ITEMS [label="1..n"];
    PRODUCTS -> ORDER_ITEMS [label="1..n"];
}

JSON Format

Generates structured JSON with table and relationship metadata:

{
  "schema": "MYSCHEMA",
  "tables": [
    {
      "name": "CUSTOMERS",
      "columns": [
        {"name": "CUSTOMER_ID", "type": "INT", "isPrimaryKey": true},
        {"name": "NAME", "type": "VARCHAR", "isPrimaryKey": false},
        {"name": "EMAIL", "type": "VARCHAR", "isPrimaryKey": false}
      ]
    }
  ],
  "relationships": [
    {
      "from": "CUSTOMERS",
      "to": "ORDERS",
      "foreignKey": "CUSTOMER_ID",
      "cardinality": "1..n"
    }
  ]
}

Examples

Basic Usage

hana-cli erdDiagram --schema MYSCHEMA --format mermaid --output erd.md

Related Commands

• calcViewAnalyzer - Analyze calculation view performance and metadata
• schemaClone - Clone schema structure and related artifacts
• graphWorkspaces - Work with graph workspace metadata and relationships

See the Commands Reference for other commands in this category.

See Also

• Category: Analysis Tools
• All Commands A-Z