what is union operator in sql code example

Example 1: sql server union all example

SELECT expression1, expression2, ... expression_n
FROM tables
[WHERE conditions]
UNION ALL
SELECT expression1, expression2, ... expression_n
FROM tables
[WHERE conditions];

Example 2: union in sql

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