rt，最近写了个update语句，条件用到了自连接，于是将代码顺理成章地写成了这样：
莫非update语句不支持别名？结果改成一般的连接，运行成功，之后尝试修改代码，变成
1
update ValidNodes
2set ItemValid=0
3from ValidNodes as v1
4inner join ValidNodes as v2 on v1.Parent=v2.ItemID
5where v2.ItemValid=0 and v1.ItemValid=1
结果编译通过，运行时报错，提示第一行update语句后面的表 'ValidNodes' 不明确update ValidNodes2
set ItemValid=03
from ValidNodes as v14
inner join ValidNodes as v2 on v1.Parent=v2.ItemID5
where v2.ItemValid=0 and v1.ItemValid=1莫非update语句不支持别名？结果改成一般的连接，运行成功，之后尝试修改代码，变成
1update ValidNodes
2set ItemValid=0
3from ValidNodes
4join ValidNodes as v2 on ValidNodes.Parent=v2.ItemID
5where v2.ItemValid=0 and ValidNodes.ItemValid=1
执行通过，汗～
update ValidNodes2
set ItemValid=03
from ValidNodes4
join ValidNodes as v2 on ValidNodes.Parent=v2.ItemID5
where v2.ItemValid=0 and ValidNodes.ItemValid=1