在SQL中是否可以在WITH中使用WITH

在SQL中，是否可以将WITH放在WITH中

以下面的查询为例

WITH Temp ([Description], [Amount], [OverdueBy])
AS 
(select Description, SUM(Amount) as Amount, (DATEDIFF(day,DueDate,GETDATE())) as OverdueBy  from brvAPAllInvoices 
Where PaidDate is null and APCo = 1 and Amount > 0 
Group By Description, DueDate, APRef

)

select * from Temp

我想基于上述查询创建一个“虚拟”临时表。是否可以使用另一个WITH将其包含在中

大致如下：

WITH Temp2 ([Description], [Amount], [OverdueBy])
AS
(
WITH Temp ([Description], [Amount], [OverdueBy])
AS 
(select Description, SUM(Amount) as Amount, (DATEDIFF(day,DueDate,GETDATE())) as OverdueBy  from brvAPAllInvoices 
Where PaidDate is null and APCo = 1 and Amount > 0 
Group By Description, DueDate, APRef

)

select * from Temp)

select * from Temp2

---

不，不能在CTE中定义CTE，但可以在一条语句中定义多个CTE并引用其他CTE

; with a as (
    select * from some_table
),
b as (
   select * 
   from another_table t
     inner join a ON (t.key = a.key)
)
select * 
from b

---

您通常会执行以下操作：

WITH Temp ([Description], [Amount], [OverdueBy])
AS 
(select Description, SUM(Amount) as Amount, (DATEDIFF(day,DueDate,GETDATE())) as OverdueBy  from brvAPAllInvoices 
Where PaidDate is null and APCo = 1 and Amount > 0 
Group By Description, DueDate, APRef
), Temp2 ([Description], [Amount], [OverdueBy]) AS 
(
    SELECT * FROM Temp
)
select * from Temp2

---

尽管在您设计的示例中，这显然没有多大用处，因为两个表结构几乎相同。我倾向于认为CTE更像是命名的派生表，而不是临时表……尽管它们不仅仅是一个派生表，这取决于您的dbms，但您可以有多个WITH语句，嵌套或不嵌套。（以PostgreSQL为例）。（搜索CTE_查询_定义。）

嵌套的

with today as (
  with yesterday as (select current_date - interval '1' day as yesterday)
  select yesterday + interval '1' day as today from yesterday 
)
select cast(today as date) from today

with yesterday as (
  select current_date - interval '1' day as yesterday
), 
today as (
  select yesterday + interval '1' day as today from yesterday 
)
select cast(yesterday as date) as dates from yesterday
union all
select cast(today as date) from today

错误：关系“昨天”不存在

---

尝试时发生了什么？Msg 156，级别15，状态1，第4行关键字“WITH”附近的语法不正确。Msg 319，15级，状态1，第4行关键字“with”附近语法不正确。如果此语句是公共表表达式、xmlnamespaces子句或更改跟踪上下文子句，则前一条语句必须以分号终止。Msg 102，第15级，状态1，第12行“'）附近的语法不正确。请确保使用实际使用的RDBMS进行标记。

with today as (
  with yesterday as (select current_date - interval '1' day as yesterday)
  select yesterday + interval '1' day as today from yesterday 
)
select * from yesterday

ERROR: relation "yesterday" does not exist

with yesterday as (
  select current_date - interval '1' day as yesterday
), 
today as (
  select yesterday + interval '1' day as today from yesterday 
)
select cast(yesterday as date) as dates from yesterday
union all
select cast(today as date) from today

dates -- 2014-06-10 2014-06-11

with today as (
  select yesterday + interval '1' day as today from yesterday 
),
yesterday as (
  select current_date - interval '1' day as yesterday
) 
select yesterday from yesterday
union all
select today from today

ERROR: relation "yesterday" does not exist