MINUS(差集)
代码：
WITH A AS (
SELECT '1' AS num FROM dual UNION
SELECT '2' AS num FROM dual UNION
SELECT '3' AS num FROM dual UNION
SELECT '4' AS num FROM dual UNION
SELECT '5' AS num FROM dual UNION
SELECT '6' AS num FROM dual UNION
SELECT '7' AS num FROM dual UNION
SELECT '8' AS num FROM dual UNION
SELECT '9' AS num FROM dual ), B AS (
SELECT '6' AS num FROM dual UNION
SELECT '7' AS num FROM dual UNION
SELECT '8' AS num FROM dual UNION
SELECT '9' AS num FROM dual UNION
SELECT '10' AS num FROM dual UNION
SELECT '11' AS num FROM dual UNION
SELECT '12' AS num FROM dual UNION
SELECT '13' AS num FROM dual UNION
SELECT '14' AS num FROM dual UNION
SELECT '15' AS num FROM dual