A MySQL to PostgreSQL migration 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.
MySQL to PostgreSQL migration: 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 handle your MySQL to PostgreSQL migration
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.
Common MySQL to PostgreSQL migration gotchas
Beyond types and keys, a MySQL to PostgreSQL migration trips on a few smaller differences. MySQL's unsigned integers have no PostgreSQL equivalent, so a larger signed type is usually needed to hold the same range. ENUM columns become a CHECK constraint or a native enum type. Identifier quoting changes from backticks to double quotes, and unquoted names fold to lower case in PostgreSQL, so mixed-case table names need care. Comparisons also behave differently, because MySQL converts values between types more loosely, which can change query results even when the schema converts cleanly.
Try FoxSchema
FoxSchema compares and migrates schemas between MySQL, PostgreSQL, and 8 other dialects. Download the app or run it in Docker.
Further reading: for more on MySQL to PostgreSQL migration, see the PostgreSQL documentation and the MySQL reference manual.
