UNION Operator

The UNION operator is used to combine the result-set of two or more SELECT statements.

Notice that each SELECT statement within the UNION must have the same number of columns. The columns must also have similar data types. Also, the columns in each SELECT statement must be in the same order.

SELECT column_name(s) FROM table1
 

UNION
 

SELECT column_name(s) FROM table2;

Note: The UNION operator selects only distinct values by default. To allow duplicate values, use the ALL keyword with UNION.

SELECT column_name(s) FROM table1
 

UNION ALL
 

SELECT column_name(s) FROM table2;