What is UNION operator? How does it work?

SQLite - Interview Questions

SQLite UNION Operator is used to combine the result set of two or more tables using SELECT statement. Both the tables must have same number of fields in result table.

Syntax :

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