CREATE TABLE T1 (x INTEGER PRIMARY KEY)
INSERT INTO T1 VALUES (1)
INSERT INTO T1 VALUES (2)

CREATE TABLE T2 (x INTEGER PRIMARY KEY)
INSERT INTO T2 VALUES (2)
INSERT INTO T2 VALUES (4)


Method 1:

SELECT COALESCE(T1.x, T2.x)
FROM T1
FULL JOIN T2
ON T1.x = T2.x
WHERE T1.x IS NULL OR T2.x IS NULL


Method 2:

SELECT x
FROM
(SELECT x
FROM T1
UNION ALL
SELECT x
FROM T2) AS T
GROUP BY x
HAVING COUNT(*)=1

--
David Portas
------------
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--