How to select date from datetime column?

I have a column of type “datetime” with values like 2009-10-20 10:00:00

I would like to extract date from datetime and write a query like:

SELECT * FROM 
data 
WHERE datetime="2009-10-20" 
ORDER BY datetime DESC

Is the following the best way to do it?

SELECT * FROM 
data 
WHERE datetime BETWEEN('2009-10-20 00:00:00' AND '2009-10-20 23:59:59')
ORDER BY datetime DESC

This however returns an empty resultset. Any suggestions?