Convert datetime value into string
This is super old, but I figured I'd add my 2c. DATE_FORMAT does indeed return a string, but I was looking for the CAST function, in the situation that I already had a datetime string in the database and needed to pattern match against it:
http://dev.mysql.com/doc/refman/5.0/en/cast-functions.html
In this case, you'd use:
CAST(date_value AS char)
This answers a slightly different question, but the question title seems ambiguous enough that this might help someone searching.
Try this:
concat(left(datefield,10),left(timefield,8))10 char on date field based on full date
yyyy-MM-dd.8 char on time field based on full time
hh:mm:ss.
It depends on the format you want it. normally you can use script above and you can concat another field or string as you want it.
Because actually date and time field tread as string if you read it. But of course you will got error while update or insert it.