Syntax for the DBA commands CREATE AUTHORIZATION and ALTER AUTHORIZATION have changed. Previously, you did not have to surround the chosen password with single quotes. Effective in version 6.4, you must surround the password with single quotes.
The DML commands INSERT, UPDATE, CREATE TABLE, and DROP TABLE are transactional commands. Previously, they were performed with auto-commit.
Syntax for the DROP DB, DROP SCHEMA commands with cascade recursion has changed.