Change the character set of a MySQL table

-- Take a dump first: CONVERT TO rewrites every row, and on MyISAM there is
-- nothing to roll back to if it stops halfway.
ALTER TABLE orders CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;

-- DEFAULT CHARACTER SET on its own only affects columns added afterwards.
ALTER TABLE orders DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci;