In Oracle, nulls in calculations involving aggregate functions are ignored
SQL> -- create demo table
SQL> create table Employee(
2 empno Number(3) NOT NULL, -- Employee ID
3 ename VARCHAR2(10 BYTE), -- Employee Name
4 hireDate DATE, -- Date Employee Hired
5 orig_salary Number(8,2), -- Orignal Salary
6 curr_salary Number(8,2), -- Current Salary
7 region VARCHAR2(1 BYTE) -- Region where employeed
8 )
9 /
Table created.
SQL>
SQL> -- prepare data for employee table
SQL> insert into Employee(empno, ename, hireDate, orig_salary, curr_salary, region)
2 values(122,'Alison',to_date('19960321','YYYYMMDD'), 45000, 48000, 'E')
3 /
1 row created.
SQL> insert into Employee(empno, ename, hireDate, orig_salary, curr_salary, region)
2 values(123, 'James',to_date('19781212','YYYYMMDD'), 23000, 32000, 'W')
3 /
1 row created.
SQL> insert into Employee(empno, ename, hireDate, orig_salary, curr_salary, region)
2 values(104,'Celia',to_date('19821024','YYYYMMDD'), 53000, NULL, 'E')
3 /
1 row created.
SQL> insert into Employee(empno, ename, hireDate, orig_salary, curr_salary, region)
2 values(105,'Robert',to_date('19840115','YYYYMMDD'), 31000, 36000, 'W')
3 /
1 row created.
SQL> insert into Employee(empno, ename, hireDate, orig_salary, curr_salary, region)
2 values(116,'Linda', to_date('19870730','YYYYMMDD'), 43000, NULL, 'E')
3 /
1 row created.
SQL> insert into Employee(empno, ename, hireDate, orig_salary, curr_salary, region)
2 values(117,'David', to_date('19901231','YYYYMMDD'), 78000, 85000, 'W')
3 /
1 row created.
SQL> insert into Employee(empno, ename, hireDate, orig_salary, curr_salary, region)
2 values(108,'Jode', to_date('19960917','YYYYMMDD'), 21000, NULL, 'E')
3 /
1 row created.
SQL>
SQL> select * from employee;
EMPNO ENAME HIREDATE ORIG_SALARY CURR_SALARY R
---------- ---------- --------- ----------- ----------- -
122 Alison 21-MAR-96 45000 48000 E
123 James 12-DEC-78 23000 32000 W
104 Celia 24-OCT-82 53000 E
105 Robert 15-JAN-84 31000 36000 W
116 Linda 30-JUL-87 43000 E
117 David 31-DEC-90 78000 85000 W
108 Jode 17-SEP-96 21000 E
7 rows selected.
SQL>
SQL> -- In Oracle, nulls in calculations involving aggregate functions are ignored
SQL>
SQL> SELECT ename, curr_salary
2 FROM employee
3 UNION
4 SELECT 'The average .......', average
5 FROM
6 (SELECT avg(curr_salary) average
7 FROM employee);
ENAME CURR_SALARY
------------------- -----------
Alison 48000
Celia
David 85000
James 32000
Jode
Linda
Robert 36000
The average ....... 50250
8 rows selected.
SQL>
SQL>
SQL>
SQL> -- clean the table
SQL> drop table Employee
2 /
Table dropped.
SQL>
SQL>
SQL>
SQL>
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