求SQL语句

数据库表table有TimeA和TimeB两个字段，TimeA不能为NULL，TimeB能为NULL，两个字段均为时间数据类型。现要求写条SQL语句，如果TimeB为空则取TimeA的值，否则取TimeB的值，按时间的降序排列。

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SQL code:
select Time=case when TimeB is null then TimeA else TimeB end
from tb
order by case when TimeB is null then TimeA else TimeB end desc

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SQL code:

select Time=isnull(TimeB,TimeA)from tb
order by Time decs

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SQL code:
select
case when TimeB is null then TimeA else TimeB end as time
from
tb
order by
case when TimeB is null then TimeA else TimeB end desc

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SQL code:

select Time=case when TimeB is null then TimeA else TimeB end
from tb
order by case when TimeB is null then TimeA else TimeB end desc

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SQL code:

select [Time]=isnull(TimeB,TimeA)from tb
order by [Time] desc

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SQL code

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