Question

我需要从数据库表中获取固定长度值。以下是查询

 select cast(TrackID as char(4)) as TrackID ,
 cast(Tracknumber as char(5)) as Tracknumber 
 from Tracking

当列值为null或为空时，我希望显示相同数量的零。

TrackID -- TrackNumber

2121    --   34343

3423    --   00000

Answer 1

您可以使用coalesce() / case：

select cast(TrackID as char(4)) as TrackID ,
       coalesce(cast(Tracknumber as char(5)), '00000') as Tracknumber 
from Tracking;

需要强制转换，因此结果是字符串，而不是数字。

如果没有NULL，“数字”不能为“空”。如果该值实际上是一个字符串，那么您需要稍微复杂的逻辑：

select cast(TrackID as char(4)) as TrackID ,
       (case when Tracknumber is null or Tracknumber = ''
             then '00000'
             else cast(Tracknumber as char(5))
        end) as Tracknumber 
from Tracking;

Answer 2

就这样做......

 select cast(TrackID as char(4)) as TrackID ,
 isnull(nullif(cast(Tracknumber as char(5)),''),'00000') as Tracknumber 
 from Tracking

当select for Fixed length返回null时显示零

2 个答案: