How to use the UNION operator in Oracle to join two similar tables

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It sure is possible, as seen in the following example:

SELECT col1, col2, col3 FROM table1
UNION 
SELECT col1, col2, col3 FROM table2;

You can even use the UNION operator on two tables that have different numbers of columns, so long as you fill in the missing columns with NULL values as can be seen below:

SELECT col1, NULL as col2, col3 FROM table1
UNION
SELECT col1, col2, NULL as col3 FROM table2;