Answers for "mysql change default value for column"

altering the column name in MySQL to have a default value

ALTER TABLE table_name ALTER COLUMN column_name SET DEFAULT 'literal';

mysql how to change default charset

ALTER DATABASE databasename CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
ALTER TABLE tablename CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;