Too many times on this forum we have explainded that using as
COMTECH001
or
COMSCI001
means bad design of table. Please, use "search" box in the right-top corner of this page.
2 reasons:
1) It's not possible to auto-increment.
2) It's limited to 999 (because of 3 places for numeric values)
Read more:
http://msdn.microsoft.com/en-us/library/ms186775.aspx[
^]