What is a set operation? code example

Example: set operations

UNION ALL:
COMBINES THE RESULT OF 2 QUERY AND
DOESN'T REMOVE DUPLICATE ROWS
AND DOESN'T SORT BY FIRST COLUMN

UNION:
COMBINES THE RESULT OF 2 QUERY AND
REMOVES DUPLICATE ROWS AND
SORTS BY FIRST COLUMN 

MINUS:
MINUS RETURNS THE LEFT NON MATCHING
DATA AS A RESULT.


INTERSECT:
BASICALLY INTERSECT COMBINES COMMON
ELEMENTS OF BOTH TABLES