SQL Sever删除外键

declare @sql varchar(max),
@tab_name varchar(128),
@fk_name varchar(128);
declare c cursor for
select OBJECT_NAME(f.parent_object_id), name
from sys.foreign_key_columns f join sys.objects o on f.constraint_object_id=o.object_id
where f.parent_object_id=object_id('sa_UserMaster')

open c
fetch next from c into @tab_name, @fk_name
while @@FETCH_STATUS=0
begin
set @sql='';
set @sql='alter table ' + @tab_name + ' drop constraint ' + @fk_name
print @sql
exec(@sql)

fetch next from c into @tab_name, @fk_name
end
close c
deallocate c