在连接中使用子选择来更新表？

Question

我正在尝试使用子选择更新具有列别名的表。问题是当我添加一个内部连接时，脚本会中断：

此更新有效，但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

但是当我添加 join 时它会中断：

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，但我需要一个额外的num / den 存储库。以下将不起作用：

;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，但我仍然无法使用最终值“总计”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

Answer 1

首先，这个示例：

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。你可以通过指定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 尚不作为可用名称存在。您可以通过多种方式解决此问题，但一种选择是在多个 CTE 中分层查询：

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

另一种选择是重复表达式：

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