Ferrule

The collar that joins you to your data.

Ferrule is a Rust-native command-line tool for querying relational databases. One static binary speaks PostgreSQL, MySQL, MSSQL, and SQLite. Oracle is optional via a feature flag.

Why ferrule?

Most database CLIs are tied to one engine — psql for Postgres, mysql for MySQL, sqlcmd for MSSQL, sqlite3 for SQLite. Each is excellent at its own backend, but moving between them means learning five output conventions, five auth quirks, and five sets of introspection commands.

Ferrule trades some backend-specific depth for a single consistent interface across all of them:

• One static binary, zero runtime dependencies for the four default backends. No libpq, no libmysqlclient, no unixodbc. The binary drops onto a fresh box and works.
• A unified type system. Every backend maps native types into a single Value enum, so a JSON dump from Postgres and a JSON dump from MySQL look identical to your downstream tools. See Concepts.
• Pipe-friendly defaults. JSON output by default, with --format table for human-readable terminal use, plus CSV / YAML / raw for pipelines.
• Same command surface across backends. ferrule query, ferrule tables, ferrule describe, ferrule explain all work the same way against any supported backend.
• Real credential hygiene. Passwords resolved through OS keyring, Docker secrets, env vars, or interactive prompt — never required in URLs, never logged. See Security.

When to reach for something else

Ferrule isn’t trying to replace the native shells when you need their specialty features. Reach for:

• psql — when you need backslash commands like \dt+, \copy, or psql variables; or when you want the deepest Postgres introspection.
• mysql / mysqlsh — for MySQL-specific tooling like mysqldump, X Protocol, or replication management.
• sqlcmd / sqlpackage — for MSSQL deployment artifacts and T-SQL debugging.
• A GUI (DBeaver, TablePlus, DataGrip) — when you want a visual ER diagram, an inline result-set editor, or stored-procedure authoring with syntax help.
• usql — if you specifically need the Go ecosystem and a built- in ORM-like layer.

Ferrule is for terminal-first, scriptable, multi-backend work: ad-hoc queries during oncall, sanity checks across staging and production replicas, fixture export/import, daily KPI bookmarks, small data pipelines.

One-minute demo

# SQLite works out of the box — no setup
ferrule query "sqlite::memory:" "SELECT 1 + 1 AS answer;" --format table

# Postgres (requires running server)
ferrule query "postgres://user:pass@localhost/db" "SELECT * FROM users;"

# Save a connection, then reuse the name
ferrule conn add prod "postgres://app@db.example.com/myapp"
ferrule conn set-password prod
ferrule query prod "SELECT COUNT(*) FROM orders;"

# Interactive REPL
ferrule repl prod
> SELECT count(*) FROM orders WHERE created_at > now() - interval '1 day';
> \format table
> \q

Where to next

• New here? Start with Installation and the Quick Start.
• Want the mental model? Read How Ferrule Thinks — it’s the conceptual map for everything else.
• Looking up a flag? Jump to the CLI Reference.
• Something broken? Try Troubleshooting.