SQL server 修改 字段默認值

使用 sql 來更改 字段默認值,如下所示

update

declare @csname varchar(100)
declare @tablename varchar(100)
declare @coulname varchar(100) 
set @tablename='T_GWED_DistributionSNInfo'
set @coulname='CreateDate' 
--select       c.name  from sysconstraints a 
--　　inner join syscolumns b on a.colid=b.colid 
--　　inner join sysobjects c on a.constid=c.id
--　　where a.id=object_id(@tablename) 
--　　and b.name=@coulname

select  @csname=[name] 
from sysobjects t
where id=(select cdefault from syscolumns where id=object_id(N''+@tablename+'') and name=@coulname)
exec('alter table '+@tablename+' drop constraint '+@csname) 
print(@tablename)
print(@coulname)
print(@csname)
exec ('ALTER TABLE '+@tablename+' add constraint ' + @csname + '  DEFAULT (getutcdate()) FOR  '+@coulname+'')