Thanks John , Thom A and Bill .
Thom, your approach seems suitable especially for systems with not-so-high memory if we look from the memory-grant perspective. Since SQL estimates the column data-occupied length to be half, and does the memory grant , what's the magnitude of impact when it knows that the actual grants required are little more because , a varchar(12) has occupancy above 6 (8 to 12) in your example ? I mean is it a costly operation that may impact performance ?