Moving a schema from one database engine to another — a cross-dialect schema migration — is harder than a same-engine migration because every dialect has its own type system, syntax, and quirks. This guide covers what translates cleanly, what needs a human, and how to generate correct target-dialect DDL.
What "cross-dialect" actually means
Comparing Postgres to MySQL, or SQL Server to Oracle, is not just a text diff. VARCHAR, SERIAL, AUTO_INCREMENT, IDENTITY, boolean handling, and default expressions all differ. A naive comparison flags equivalent types as changes and produces DDL the target rejects.
What translates cleanly
- Tables and columns — structural, with type mapping between dialects.
- Primary and foreign keys — structural; referenced tables are requalified to the target schema.
- Indexes and unique constraints — translated via each dialect's own
CREATE INDEXform.
A good tool is cross-dialect aware: it will not false-flag a Postgres boolean against a MySQL tinyint(1), and it maps types rather than copying them verbatim.
What needs manual review
- Views and function bodies — these are dialect-specific SQL and are not auto-translated. A cross-dialect view is flagged for manual review with the original body preserved.
- User-defined types — each engine has its own enum/domain/object model with no clean translation layer.
- Check constraints and triggers — procedural logic rarely ports one-to-one.
The key is that the tool tells you up front which object types translate cleanly and which need a look, instead of discovering it as a runtime error mid-migration.
Generating the migration
Once you understand the readiness of each object type, generate DDL targeting the destination dialect, review it, and apply it with a snapshot. Treat flagged views, types, and procedural objects as a manual checklist alongside the generated script.
One tool, ten dialects
FoxSchema supports PostgreSQL, MySQL, MariaDB, SQL Server, Azure SQL, Oracle, IBM Db2, SQLite, ClickHouse, and Amazon Redshift, with a cross-dialect readiness panel built in. Download it or read the docs to get started.
