Let us consider a table have three fields say Id,Mark,and name.and table name is student.
For getting second largest mark from student table you can use following sql query.
Step 1: get top 2 marks from student table in descending order
Select top 2 mark from student order by Mark desc
Step 2: find minimum from the inner query
Select min(mark) from (inner query)
So the final query will be
Select min(mark) from (select top 2 mark from student order by Mark desc)a