如下所示，nullFill!(t1.time, t2.time)是指若t1.time是空值，就用t2.time的值填充：
t1= table(1 2 3 3 6 as time, 1.1 2.1 3.1 3.1 6.1 as value)
t2 = table(5 3 1 as time, 5.1 3.1 1.1 as qty)
select nullFill(t1.time, t2.time) as time, value, qty from fj(t1, t2, `time) order by nullFill!(t1.time, t2.time)