SELECT CAN GO ANY WHERE

SELECT DECODE ((SELECT 'x'
FROM DUAL), (SELECT 'x'
FROM DUAL), (SELECT 'y'
FROM DUAL)) AS RESULT
FROM (SELECT 'm'
FROM DUAL)
WHERE (SELECT 1
FROM DUAL) = (SELECT 1
FROM DUAL)
AND (SELECT 2
FROM DUAL) BETWEEN (SELECT 1
FROM DUAL) AND (SELECT 3
FROM DUAL)
AND NVL ((SELECT NULL
FROM DUAL), (SELECT 'z'
FROM DUAL)) = (SELECT 'z'
FROM DUAL)
ORDER BY (SELECT 1
FROM DUAL);