ALTER DATABASE `database_name`
DEFAULT CHARACTER SET utf8mb4
DEFAULT COLLATE utf8mb4_general_ci;
ALTER TABLE table_name CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;
ALTER TABLE table_name DEFAULT CHARSET=utf8mb4;
ALTER TABLE table_name MODIFY COLUMN column_name text CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL;