Update only Time in a mysql DateTime field

Question

How can I update only the time in an already existing DateTime field in MySQL? I want the date to stay the same.

Answer 1

Asuming you have a DATE field and TIME field and want to inject the time into the date, try this:

UPDATE mytable
SET mydatefield = ADDTIME( DATE_FORMAT(mydatefield,'%Y-%m-%d 00:00:00'), mydatefield)
WHERE myid = ...