SQL timestamp between hours that fall across midnight
<p>I'm trying to find all records that would fall with in a current time period based on the current time. For example the current time is 12:30am and I need all the records from the previous day starting at 6:00pm till current time. Very new to SQL and any help would be appreciated.</p>

<p>Below is a screenshot of the table and the column of interest is the timestamp (datetime). I have not tried really anything concrete, am still struggling with just trying to figure out how I would go about it.
<a href="http://i.stack.imgur.com/vCUPW.png" rel="nofollow">Table</a></p>