Other Diagrams Example

SchemaCrawler can generate diagrams in formats beyond its built-in GraphViz generated output by combining its script command with small Python scripts. This example shows how to produce Mermaid, DBML for dbdiagram.io, and PlantUML entity-relationship diagrams.

How to Run

Before running this example, complete the setup in Getting Started.

Replace with the connection options for your chosen database. See Getting Started.

Mermaid ER Diagram

schemacrawler \
  --server postgresql \
  --host postgresql \
  --database schemacrawler \
  --user schemacrawler \
  --password schemacrawler \
  --info-level standard \
  --command script \
  --script mermaid.py \
  --output-file share/output.mmd

The output file output.mmd will appear in your working directory on the host. Paste its contents into the Mermaid Live Editor to view the diagram.

DBML for dbdiagram.io

schemacrawler \
  --server postgresql \
  --host postgresql \
  --database schemacrawler \
  --user schemacrawler \
  --password schemacrawler \
  --info-level standard \
  --command script \
  --script dbml.py \
  --output-file share/output.dbml

The output file output.dbml will appear in your working directory on the host. Paste its contents into dbdiagram.io to view and share the diagram.

PlantUML ER Diagram

schemacrawler \
  --server postgresql \
  --host postgresql \
  --database schemacrawler \
  --user schemacrawler \
  --password schemacrawler \
  --info-level standard \
  --command script \
  --script plantuml.py \
  --output-file share/output.puml

The output file output.puml will appear in your working directory on the host. Paste its contents into the PlantUML online server to render the diagram.

Replace with the connection options for your chosen database. See Getting Started.

Resource Files

The script command passes SchemaCrawler’s in-memory catalog model to a Python script. The Python script then walks the catalog’s tables and relationships and emits the diagram source text to stdout.

Python Scripts

The three Python scripts (mermaid.py, dbml.py, plantuml.py) each receive the SchemaCrawler catalog as a scripting context and emit diagram source in their respective formats:

Script	Output format	View at
mermaid.py	Mermaid erDiagram syntax	Mermaid Live Editor
dbml.py	DBML (Database Markup Language)	dbdiagram.io
plantuml.py	PlantUML @startuml entity diagram	PlantUML server

Each script iterates over the filtered tables (AUTHORS and BOOKS in the PUBLIC.BOOKS schema) and their foreign-key relationships, then serialises them in the target notation.

Place each script file in your working directory. It will be accessible inside the container as share/mermaid.py, share/dbml.py, or share/plantuml.py.

How to Experiment

1. Modify the --schemas and --tables filter options in the run command to include more (or fewer) tables in the diagram.
2. Edit the Python scripts to customise the diagram output — for example, adding column data types to the Mermaid diagram or changing the DBML colour theme.
3. Add a new Python script to emit a different diagram format (e.g., Graphviz DOT, Nomnoml) and run it the same way: schemacrawler <connection-options> ... --script share/myformat.py > share/output.txt.