Using INTERSECT operator, Oracle displays the common rows from both the SELECT statements, with no duplicates and data arranged in sorted order (ascending 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

Using INTERSECT to get the common rows from each component queries. That means INTERSECT will give you distinct rows.

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

ENAME
----------
ADAMS
SMITH