Usage and Examples of SQL UNION and UNION ALL Keywords

SQL Keyword Reference

UNION

The UNION command combines the result sets of two or more SELECT statements (only different values)

The following SQL statement retrieves cities from the 'Customers' and 'Suppliers' tables (only different values):

SELECT City FROM Customers
UNION
SELECT City FROM Suppliers
ORDER BY City;

UNION ALL

The UNION ALL command combines the result sets of two or more SELECT statements (allows duplicate values).

The following SQL statement retrieves cities from the 'Customers' and 'Suppliers' tables (also with duplicate values):

SELECT City FROM Customers
UNION ALL
SELECT City FROM Suppliers
ORDER BY City;

SQL Keyword Reference