Ryan,
First, decide whether the date column is to store date or datetime, and if the latter, whether it can be a timestamp or, if you must store datetimes before 1970 or after 2038, a datetime type. Read the manual section on date and time data types. If it is to be a timestamp, decide which default you want.
There are obvious advantages to storing dates in one column. Convenience, compactness, efficiency. There are also disadvantages. For example, MySQL does not support function-based indexes, so you may not maintain an index on, say, MONTH(datevalue). Usually that's not a problem, but it can be. Depends on your requirement.
As a beginner you need to get familiar with standard methods of database design. See
http://www.artfulsoftware.com/dbresources.html. Adopt a consistent, thorough method, eg
http://www.artfulsoftware.com/dbdesignbasics.html, and stick to it.
You can make one date column (named, say, dt) from three (named, say, y, m and d) with something like this:
ALTER TABLE tbl add column dt datetime;
UPDATE tbl SET dt=DATE(CONCAT(y,'-',m,'-',d));
-- check results
SELECT * FROM tbl;
ALTER TABLE tbl DROP COLUMN d;
ALTER TABLE tbl DROP COLUMN m;
ALTER TABLE tbl DROP COLUMN y;
PB
http://www.artfulsoftware.com