SUM
                                                            Purpose
This function returns the sum of expr within a window or group of rows.
Syntax
sum::=
                                                                        
                                                                    
Usage Notes
- With 
DISTINCT, the function considers duplicate values ofexpronly once. It considers all occurrences withALL. If the function contains neitherALLnorDISTINCT, the default isALL. - This function supports arguments of types 
numericandinterval. 
Examples
Aggregate Function
SELECT 
    department, 
   SUM(current_salary) SUM_SALARY 
FROM employee_table GROUP BY department;
                                                                Result
| DEPARTMENT | SUM_SALARY | 
| ACCOUNTS | 350000 | 
| HR | 285000 | 
Analytic Function
SELECT 
    id, department, hire_date, current_salary, 
    SUM(current_salary) OVER (PARTITION BY department ORDER BY hire_date) SUM_SALARY 
FROM employee_table ORDER BY department, hire_date;
                                                                Result
| ID | DEPARTMENT | HIRE_DATE | CURRENT_SALARY | SUM_SALARY | 
| 2005 | ACCOUNTS | 2013-01-01 | 80000 | 80000 | 
| 2003 | ACCOUNTS | 2015-07-01 | 80000 | 160000 | 
| 2002 | ACCOUNTS | 2017-01-01 | 65000 | 295000 | 
| 2004 | ACCOUNTS | 2017-01-01 | 70000 | 295000 | 
| 2001 | ACCOUNTS | 2018-07-01 | 55000 | 350000 | 
| 1003 | HR | 2014-01-01 | 90000 | 90000 | 
| 1002 | HR | 2016-01-01 | 70000 | 230000 | 
| 1004 | HR | 2016-01-01 | 70000 | 230000 | 
| 1001 | HR | 2018-01-01 | 55000 | 285000 |