Invalid column name on sql server update after column create

问题：新建一个测试表xx

select 1 as code into xx
select * from xx

给这个表添加一个列val, val列不允许为空，将表中已有的数据val值更新为1

alter table xx add val int null;

update xx set val = 1 where 1=1;

alter table xx alter column val int not null;

执行以上脚本会有以下错误：

Msg 207, Level 16, State 1, Line 2
Invalid column name 'val'.

解决办法：添加GO，说明连接

alter table xx add val int null;
GO
update xx set val = 1 where 1=1;

alter table xx alter column val int not null;

More generally the problem is a parse/compile issue. SQL Server tries to compile all statements in the batch before executing any of the statements.