WIPRO

1.can we use select statement in trigger.
2. how can we retrieve last n records
3.select clause'clauses order'means where,order by, group by..
4. write the query to get maximum salary in each department.
5. table emp has 20 records
select count(8) from emp,
 select count(2) from emp,  
select count(1) from emp,
select count(*) from emp. 
what is the output.
6. can we use commit in trigger.
7.where clause and having clause difference.
8. not null vs zero.