Migrating from MySQL to PostgreSQL is a popular move — for stronger typing, richer SQL, and better concurrency. But the two engines differ enough that a naive schema copy fails. This guide focuses on the schema layer: what changes, and how to generate DDL PostgreSQL will actually accept.
Type mapping is the first hurdle
MySQL and PostgreSQL disagree on fundamentals. TINYINT(1) is MySQL's boolean; PostgreSQL has a real boolean. MySQL's DATETIME maps to PostgreSQL timestamp. AUTO_INCREMENT columns become SERIAL/IDENTITY backed by a sequence. Unsigned integers do not exist in PostgreSQL. A migration that copies types verbatim produces invalid DDL.
Auto-increment vs sequences
In MySQL, AUTO_INCREMENT is a column attribute. In PostgreSQL, the same behaviour comes from a sequence (via SERIAL or GENERATED … AS IDENTITY). A schema-aware tool recognises the intent and emits the PostgreSQL equivalent rather than a literal translation.
What to watch for
- Case sensitivity — PostgreSQL folds unquoted identifiers to lowercase; MySQL's behaviour depends on the OS.
- ENUMs — MySQL inline enums become PostgreSQL
CREATE TYPE … AS ENUMor check constraints. - Zero dates — MySQL's
0000-00-00has no PostgreSQL equivalent. - Views and stored routines — dialect-specific SQL that will not auto-translate; treat them as a manual checklist.
Let the diff do the mapping
Rather than hand-translate, compare the MySQL schema (source) against an empty or partial PostgreSQL target and let a cross-dialect schema diff generate the PostgreSQL DDL. It maps equivalent types, requalifies foreign keys, and flags anything (views, custom types) that needs a human. See our cross-dialect migration guide for what translates cleanly.
Try FoxSchema
FoxSchema compares and migrates schemas between MySQL, PostgreSQL, and 8 other dialects. Download the app or run it in Docker.
