Aggregate Functions:

 They are used to compute a single value from a set  of attribute values of a column:

   count :

            how many rows(tuples) are stored in the relation EMP

select count(*) from EMP;

            how many different job title  are stored in the relation EMP

select count(distinct job) from EMP;

max & min:

           select min(SAL),max(SAL) from EMP

           select max(SAL)- min(SAL)  from EMP

sum:

         select sum(SAL) from EMP

avg:

PL/SQL

Structure of PL/SQL:

     Declare

              <Constants>

               <Variables>

               <Cursors>

                <User defined exceptions>

Begin

         <PL/SQL Statements>

          exception

               <exception handling>

End

Know in PL/SQL:

About

1.Exception handling

2.Procedures

3.Functions

4.assertions

5.Triggers