通过脚本添加字段不成功
/*create table test(
  lxh int,
  msg varchar(80)
)
*/

if not exists (select name from syscolumns where id = object_id('test') and name = 'ss') 
begin
  alter table test add ss int default(0);
  update test set ss = lxh;
end;
执行脚本后报错，报错信息如下：
消息 207，级别 16，状态 1，第 0 行
列名 'ss' 无效。
另：if not exists (select name from syscolumns where id = object_id('test') and name = 'ss') 
begin
  alter table test add ss int default(0);
  --update test set ss = test.lxh;
end;
执行这句脚本是成功的

------解决方案--------------------

SQL code

if not exists (select name from syscolumns where id = object_id('test') and name = 'ss')  
begin
  alter table test add ss int default(0);
  exec('update test set ss = lxh;')
end;