nERD

Interactive terminal entity-relationship diagrams built with Rust and Ratatui.

Run

From the repository root, with Rust and Cargo installed:

cargo run --locked

The application opens an interactive diagram with five e-commerce tables and four foreign-key relationships. The startup SQL is embedded from examples/sample_schemas/ecommerce.sql; no example flag or external database is required.

There is one Cargo package, nerd-core, at the repository root. The old root prototype and print-only Rust examples have been removed. The library remains available as nerd_core.

Controls

Diagram

Key	Action
Tab / Shift+Tab	Select the next / previous entity
Arrow keys	Move the selected entity
Ctrl+D	Delete the selected entity and its relationships
s	Open the SQL editor
i	Import the current SQL and recalculate layout
g	Generate SQL from the diagram and open it in the editor
n	Create a table with an id primary key
r	Recalculate layout
?	Show help
q	Quit

SQL editor

The editor opens in normal mode. Press i to insert text. In normal mode, h/j/k/l or arrow keys move the cursor, w/b move by word, 0/$ move to line boundaries, x deletes a character, and d deletes the current line.

• Ctrl+S: parse and apply SQL changes, then return to the diagram on success.
• Esc: leave insert mode; from normal mode, return to the diagram.
• Ctrl+Q: quit from normal mode.

In help, Esc or q returns to the diagram. In the table creator, type a name and press Enter, or cancel with Esc.

SQL samples

examples/sample_schemas/ contains:

• ecommerce.sql: the built-in startup sample.
• blog.sql: authors, posts, tags, and comments.
• library_with_fk.sql: books, authors, publishers, members, and loans.

Each sample declares its foreign keys in CREATE TABLE statements. To try another sample, replace the current SQL in the editor and press Ctrl+S. There is no command-line SQL file loader.

Current limitations

• SQL import handles CREATE TABLE, not ALTER TABLE. Generated foreign keys use ALTER TABLE, so exporting and re-importing SQL is not yet lossless.
• The editor's cursor operations are not Unicode-safe; non-ASCII editing can panic.
• SQL parse errors are not displayed in the UI. Invalid SQL leaves the previous diagram unchanged.
• Foreign-key routing and overlapping table placement can require manual adjustment.

Development

cargo fmt --check
cargo test --locked --all-targets
cargo clippy --locked --all-targets -- -D warnings
cargo build --locked --release

• src/main.rs: terminal lifecycle and screen composition, using the library.
• src/app.rs: interactive state and key handling.
• src/models/, src/parser/, src/layout/, src/render/, src/sync/: schema data, SQL parsing, layout, rendering, and SQL synchronization.
• tests/: foreign-key parsing regressions and rendered-diagram snapshots.

License

Apache-2.0. See LICENSE.