Azimutt is a database exploration and documentation tool made for large databases. Try Azimutt now
JSON
Not properly a database schema dialect but using the Azimutt JSON Schema structure, you will be able to define your database structure in JSON and convert it to other dialects.
Mermaid
It's a Markdown-inspired text definitions that generate flowcharts diagrams. It can be used to generate Entity-Relationship diagrams, and even has a Live Editor.