当选择查询固定长度返回空值时显示零值

Question

我需要从数据库表中获取固定长度的值。以下是查询

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

我想显示相同数量的零时列值为空或空。

TrackID -- TrackNumber 

2121 -- 34343 

3423 -- 00000 

Answer 1

只是这样做......

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

Answer 2

您可以使用coalesce()/case：需要

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

演员这样的结果是一个字符串，而不是数字。

如果不是“NULL”，“数字”不能为“空”。如果该值确实是一个字符串，那么你需要稍微更复杂的逻辑：

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;