mysql - How to alter a column and change the default value?

I got the following error while trying to alter a column's data type and setting a new default value:

ALTER TABLE foobar_data ALTER COLUMN col VARCHAR(255) NOT NULL SET DEFAULT '{}';

ERROR 1064 (42000): You have an error in your SQL syntax; check the
manual that corresponds to your MySQL server version for the right
syntax to use near 'VARCHAR(255) NOT NULL SET DEFAULT '{}'' at line 1

Answer

ALTER TABLE foobar_data MODIFY COLUMN col VARCHAR(255) NOT NULL DEFAULT '{}';

A second possibility which does the same (thanks to juergen_d):

ALTER TABLE foobar_data CHANGE COLUMN col col VARCHAR(255) NOT NULL DEFAULT '{}';