>SELECT ID FROM MyTable WHERE LName LIKE 'SM%'
>
>This returns about 12,000 records in 45 seconds.
>
>If I run this T-SQL statement:
>
>SELECT LName FROM MyTable WHERE LName LIKE 'SM%'
>
>This returns about 12,000 records in only 2 seconds! Very big difference.
>

The server is having to do a full table scan of all the IDs while comparing the LNAME parameter. In the second one only the index is being used. What do you get if you try:

SELECT LName, ID from MyTable where LName LIKE 'SM%'

and

SELECT ID, LName from MyTable where LName LIKE 'SM%'