Minus operator displays the rows which are present in the first query but absent in the second query, with no duplicates and data arranged in ascending order by default.

--1st query
SELECT Ename FROM Emp WHERE Deptno = 20;

ENAME
----------
JONES
SCOTT
FORD
SMITH
ADAMS


--2nd query
SELECT Ename FROM Emp WHERE Job = 'CLERK';

ENAME
----------
SMITH
ADAMS
JAMES
MILLER

SELECT Ename FROM Emp WHERE Deptno = 20
MINUS
SELECT Ename FROM Emp WHERE Job = 'CLERK';

ENAME
----------
FORD
JONES
SCOTT


SELECT Ename FROM Emp WHERE Job = 'CLERK'
MINUS
SELECT Ename FROM Emp WHERE Deptno = 20;

ENAME
----------
JAMES
MILLER