MySQL - Select only Date/ Time from a 'DateTime' Column

SELECT DATE_FORMAT(NOW(), '%Y-%m-%d') DATEONLY,
       DATE_FORMAT(NOW(),'%H:%i:%s') TIMEONLY

OR

select date(ColumnName) from tablename

select time(ColumnName) from tablename

MySQL - Update only Time of a 'DateTime' column

UPDATE `table` SET `date_column` = CONCAT(DATE(`date_column`), ' 23:59:59')