Create date from day, month, year fields in MySQL

The simplest way to do this is:

DATE(CONCAT_WS('-', year, month, day))

LPAD is not necessary as @pbarney pointed out earlier. If you are comparing with another date object, it's not strictly necessary to wrap it with DATE as MySQL will cast it automatically:

some_date_field > CONCAT_WS('-', year, month, day)

You can use STR_TO_DATE() function.

When you have integer values for year, month and day you can make a DATETIME by combining MAKEDATE() and DATE_ADD(). MAKEDATE() with a constant day of 1 will give you a DATETIME for the first day of the given year, and then you can add to it the month and day with DATE_ADD():

mysql> SELECT MAKEDATE(2013, 1);
+-------------------+
| MAKEDATE(2013, 1) |
+-------------------+
| 2013-01-01        |
+-------------------+

mysql> SELECT DATE_ADD(MAKEDATE(2013, 1), INTERVAL (3)-1 MONTH);
+---------------------------------------------------+
| DATE_ADD(MAKEDATE(2013, 1), INTERVAL (3)-1 MONTH) |
+---------------------------------------------------+
| 2013-03-01                                        |
+---------------------------------------------------+

mysql> SELECT DATE_ADD(DATE_ADD(MAKEDATE(2013, 1), INTERVAL (3)-1 MONTH), INTERVAL (11)-1 DAY);
| DATE_ADD(DATE_ADD(MAKEDATE(2013, 1), INTERVAL (3)-1 MONTH), INTERVAL (11)-1 DAY) |
+----------------------------------------------------------------------------------+
| 2013-03-11                                                                       |
+----------------------------------------------------------------------------------+

So to answer the OP's question:

SELECT * FROM `date`
WHERE DATE_ADD(DATE_ADD(MAKEDATE(year, 1), INTERVAL (month)-1 MONTH), INTERVAL (day)-1 DAY)
BETWEEN '2013-01-01' AND '2014-01-01';

To build a sortable date string from that, you'll need CONCAT to join the bits together and LPAD to make sure the month and day fields are two digits long. Something like this:

CONCAT(`year`,'-',LPAD(`month`,2,'00'),'-',LPAD(`day`,2,'00'))

Once you have that, you should be able to use BETWEEN, as they'll be in a sortable format. However if you still need to convert them to actual datetime fields, you can wrap the whole thing in UNIX_TIMESTAMP() to get a timestamp value.

So you'd end up with something like this:

SELECT UNIX_TIMESTAMP(CONCAT(`year`,'-',LPAD(`month`,2,'00'),'-',LPAD(`day`,2,'00'))) as u_date
WHERE u_date BETWEEN timestamp_1 and timestamp_2

However, be aware that this will be massively slower than if the field was just a simple timestamp in the first place. And you should definitely make sure you have an index on the year, month and day fields.