Set Operators

Same column count and compatible types.

Column names come from the first query.

A single ORDER BY goes at the end.

All set operators have equal precedence (evaluated top-down). Use parentheses.

SELECT city FROM customers UNION      SELECT ship_city FROM orders;   -- distinct
SELECT city FROM customers UNION ALL  SELECT ship_city FROM orders;   -- keeps duplicates
SELECT customer_id FROM customers INTERSECT SELECT customer_id FROM orders;
SELECT customer_id FROM customers MINUS     SELECT customer_id FROM orders;
SELECT customer_id FROM customers EXCEPT    SELECT customer_id FROM orders;   -- 21c+ synonym
SELECT ... INTERSECT ALL / MINUS ALL / EXCEPT ALL ...;                          -- 21c+