# use-db-constraint
Constraint references, kinds, metadata, check labels, status, and deferrability.
This crate is part of the use-database facade workspace. It provides small,
engine-neutral vocabulary types and metadata containers. It does not connect to
databases, execute queries, run migrations, parse SQL, or model engine-specific
behavior.
## Example
~~~rust
use use_db_constraint::CheckExpressionLabel;
let label = CheckExpressionLabel::new("positive balance").expect("valid label");
assert_eq!(label.as_str(), "positive balance");
~~~