Also, use proper types for your columns. Numeric values -like a salary- should not be entered as strings. If you store them as strings the values may not sort as you would expect. For example:

select max(salary)

from (

select '20' as salary

union all select '100'

) t

The output of this is:

----

20

(1 row(s) affected)

Probably not what you wanted, is it?