sqldef

sqldef is a free command-line tool for teams that want to manage relational database changes in SQL. It is at its best when a team can treat a complete schema file as the desired state and use repeatable comparisons in deployment workflows. Choose it for that SQL-first, multi-engine approach; look elsewhere if a graphical workspace is central to how you manage databases.

Overview

Keep the complete schema you want in a SQL file, and sqldef compares it with the current database to generate and apply the required DDL. This shifts the workflow away from maintaining each migration step by hand. Its idempotent operations are useful in recurring deployments: once the database matches the file, running the command again produces no changes. That repeatability helps make schema updates predictable, though teams still need to review proposed changes as part of their own release process.

Supported engines include MySQL, MariaDB, TiDB, PostgreSQL, SQL Server, and SQLite3. That range can help teams standardize their schema-change workflow across different relational databases, but it does not make SQL portable between them; schemas must still fit their target engines.

Key features

• Declarative schema comparison: Compare a complete desired schema with the current database, then generate and apply DDL changes. This suits teams that prefer describing the end state over tracking every edit as a separate migration step.
• Dry-run and export: Export the current schema and preview migrations without executing them. That gives developers a chance to inspect proposed changes before applying them, rather than making a preview depend on a live alteration.
• Offline comparison: Compare two SQL files without connecting to a database. This makes sqldef useful for validating schema changes in CI/CD or generating migration scripts before a database is involved.
• Rename annotations: An @renamed annotation documents renames of tables, columns, indexes, and ENUM values. That gives the comparison workflow an explicit way to represent changes that might otherwise be interpreted differently.
• Repeatable commands: Operations are safe to run more than once, and a database already aligned with the desired schema yields no changes. This is a practical fit for automated workflows that may invoke the same operation repeatedly.
• Single-binary distribution: Each database tool is distributed as a binary without dependencies, reducing setup requirements. Docker images and a GitHub Action for previewing schema changes also provide options for containerized and CI workflows.

Pricing

sqldef is free: its plan costs nothing. It is an open-source CLI tool under the MIT License, with the parser under Apache License 2.0. There is no free trial to weigh against a paid tier; the tool itself is the free offering.

That makes it an accessible option for individuals and teams without a per-seat or subscription cost. The trade-off is the command-line, SQL-based workflow: the free price does not turn it into a visual database management environment.

Platforms

sqldef is cross-platform, with support for Linux, macOS, Windows, and self-hosted use. Linux users can choose prebuilt binaries or Docker images, though Debian packages are not available. On macOS, the Homebrew tap covers mysqldef, psqldef, sqlite3def, and mssqldef. The project also links to a GitHub Action for previewing changes, which is useful for teams that want schema checks in CI/CD.

Who it's for

sqldef suits developers and database teams comfortable writing SQL and working from the command line. It is particularly relevant when a team wants one desired-state workflow for supported relational databases, or needs to compare SQL files offline as part of validation and migration-script generation. It is a weaker fit for people who want a graphical interface or prefer to manage changes through a visual editor.

Pros and cons

• Pro: A complete desired schema drives generated DDL, reducing the need to maintain every change as a separate hand-written migration step.
• Pro: Dry-run previews, offline file comparison, and repeatable operations support review and automation before changes reach a database.
• Pro: Six supported database engines and a no-dependency binary distribution make the tool relevant across varied SQL environments.
• Con: The workflow is SQL and command-line centered, so it is not the right choice for readers who need visual schema management.
• Con: Support across multiple engines does not make schemas interchangeable; teams must still account for each database's SQL.
• Con: Linux users looking specifically for a Debian package will need to use another distribution route.

Alternatives

For a free PostgreSQL schema diff tool, apgdiff is a narrower option; sqldef is the better fit when support for several database engines matters. Choose dbForge Studio for PostgreSQL instead if you want a freemium PostgreSQL tool with a free trial and features such as context-aware code completion, query history, a visual data editor, and data export and import.

Skeema is worth considering for MySQL-focused teams that want table, stored procedure, and function support plus 18 linter checks in its free Community plan; its Plus plan is $124 a month. pgquarrel is another free alternative for readers comparing PostgreSQL schemas.

driftcurve is a free self-hosted option with no subscription and no accounts in its default local mode. UserFolderMigrator is a free, Windows-only alternative. DBC is another free option for Linux, macOS, and Windows users, while dbdiff is a free alternative available for Linux, macOS, Windows, and self-hosted use. Browse Database Schema Comparison Tools for more options.

Verdict

Choose sqldef if you want a free, repeatable SQL workflow for generating, previewing, and applying schema changes across multiple relational engines. Its strongest advantage is combining desired-state comparison with offline checks and automation-friendly operations. Look elsewhere if your priority is a graphical interface or a workflow that hides SQL and command-line work.