Merging two columns?

Question

MySQL

I have three columns: date, time and datetime which have the following format:
date = 2013-03-02
time =
21:48:00 datetime = 000-00-00 00:00:00
Please tell me how to compose correctly SQL query so that you can simply execute it in phpMyAdmin and the data from the date and time columns would be saved in datetime and there it would be 2013-03-02 21:48:00

Answer 1

UPDATE table SET `datetime`=CONCAT(`date`,' ',`time`)