Sql server 是否在联接中使用subselect更新表？

我正在尝试使用subselect更新具有列别名的表。问题是，当我添加内部联接时，脚本会中断：

此更新有效，但与子选择没有内部联接：

declare @erase table
(
id varchar(10),
total int
)
insert into @erase (id) select 'x'

declare @var1 int = 10
declare @var2 int = 10
declare @var3 int = 10
declare @var10 int = 10
declare @var11 int = 10
declare @var12 int = 10

update @erase 
set id = num / den
FROM
(
    select 
    'x' as id,
    @var1 * @var2 * @var3 * @var10* @var11* @var12 as 'num',
    @var1 + @var2 + @var3 + @var10+ @var11+ @var12 as 'den'
) as innerTable

但当我添加一个

连接时，它会断开：

declare @erase table
(
id varchar(10),
total int
)
insert into @erase (id) select 'x'

declare @var1 int = 10
declare @var2 int = 10
declare @var3 int = 10
declare @var10 int = 10
declare @var11 int = 10
declare @var12 int = 10

update @erase 
set id = innerTable.num / innertable.den
from @erase inner join innertable on
@erase.id = innertable.id
FROM
(
    select 
    'x' as id,
    @var1 * @var2 * @var3 * @var10* @var11* @var12 as 'num',
    @var1 + @var2 + @var3 + @var10+ @var11+ @var12 as 'den'
) as innerTable

我想使用
cte
，但我需要为
num/den
添加一个存储库。以下操作将不起作用：

;with cte as
(
    select 
    'x' as id,
    @var1 * @var2 * @var3 * @var10* @var11* @var12 as 'num',
    @var1 + @var2 + @var3 + @var10+ @var11+ @var12 as 'den',
    num / den as 'total' -- will break
)
update @erase 
set total = cte.total
from @erase inner join cte on
@erase.id = cte.id

如何在生成
num/den
的同一事务中更新
@erase

编辑：
我找到了解决方法，但仍无法使用最终值“total”进行更新：

;with cte as
(
    select 
    'x' as id,
    @var1 * @var2 * @var3 * @var10* @var11* @var12 as 'num',
    @var1 + @var2 + @var3 + @var10+ @var11+ @var12 as 'den',
    num / den as 'total' -- will break
)
update @erase 
set total = num / den --Although I prefer using alias total.
from @erase inner join cte on
@erase.id = cte.id

首先，这个样本：

update @erase 
set id = innerTable.num / innertable.den
from @erase inner join innertable on
@erase.id = innertable.id
FROM
(
    select 
    'x' as id,
    @var1 * @var2 * @var3 * @var10* @var11* @var12 as 'num',
    @var1 + @var2 + @var3 + @var10+ @var11+ @var12 as 'den'
) as innerTable

这里的问题是有两个FROM子句。您可以通过指定
innertable
inline来修复它，如下所示：

update @erase 
set id = innerTable.num / innertable.den
from @erase 
inner join (
    select 
    'x' as id,
    @var1 * @var2 * @var3 * @var10* @var11* @var12 as num,
    @var1 + @var2 + @var3 + @var10+ @var11+ @var12 as den
) innertable on @erase.id = innertable.id

然后是CTE版本：

with cte as
(
    select 
    'x' as id,
    @var1 * @var2 * @var3 * @var10* @var11* @var12 as 'num',
    @var1 + @var2 + @var3 + @var10+ @var11+ @var12 as 'den',
    num / den as 'total' -- will break
)

这里的问题是
total
行上的
num
和
den
尚未作为可用名称存在。您可以通过多种方式解决此问题，但有一种方法是将查询分层到多个CTE中：

with cte1 as
(
    select 
    'x' as id,
    @var1 * @var2 * @var3 * @var10* @var11* @var12 as num,
    @var1 + @var2 + @var3 + @var10+ @var11+ @var12 as den,
), 
cte2 As (
    select *,  num/den as total from cte1
)
update @erase 
set total = cte2.total
from @erase 
inner join cte2 on @erase.id = cte2.id

另一个选项是重复表达式：

with cte as
(
    select 
    'x' as id,
    @var1 * @var2 * @var3 * @var10* @var11* @var12 as num,
    @var1 + @var2 + @var3 + @var10+ @var11+ @var12 as den,
    ( @var1 * @var2 * @var3 * @var10* @var11* @var12 )
      / 
    ( @var1 + @var2 + @var3 + @var10+ @var11+ @var12 ) as total
)
update @erase 
set total = cte.total
from @erase 
inner join cte on @erase.id = cte.id

非常感谢你。