select sum(decode(t.department, 'A', t.C, 0)) as f_e10 from test t where t.date_num = &date_1 select sum(decode(t.department, 'A', t.C, 0)) as f_e11 from test t where t.date_num = &date_2 就是上面这两个结果集,只是由于日期不同,导致C字段结果不同,现在想求两天的差值,该怎么把这两段SQL组合起来呢? 求大神指点