创建新的条件相当于创建了新的字表
SELECT
a.s_no
FROM
(
SELECT
s_no,
score
FROM
SC
WHERE
c_no = ‘001‘
) a,
(
SELECT
s_no,
score
FROM
SC
WHERE
c_no = ‘002‘
) b
WHERE
a.score > b.score
AND a.s_no = b.s_no;
原文：http://www.cnblogs.com/ybbd/p/6358028.html