不支持嵌套的'With'，但你总是可以使用第二个With作为子查询，例如:

WITH A AS (
                --WITH B AS ( SELECT COUNT(1) AS _CT FROM C ) SELECT CASE _CT WHEN 1 THEN 1 ELSE 0 END FROM B --doesn't work
                SELECT CASE WHEN count = 1 THEN 1 ELSE 0 END AS CT FROM (SELECT COUNT(1) AS count FROM dual)
                union all
                select 100 AS CT from dual
           )
              select CT FROM A

我们可以创建嵌套的cte。请看下面的例子

;with cte_data as 
(
Select * from [HumanResources].[Department]
),cte_data1 as
(
Select * from [HumanResources].[Department]
)

select * from cte_data,cte_data1

您可以执行以下操作，这被称为递归查询:

WITH y
AS
(
  SELECT x, y, z
  FROM MyTable
  WHERE [base_condition]

  UNION ALL

  SELECT x, y, z
  FROM MyTable M
  INNER JOIN y ON M.[some_other_condition] = y.[some_other_condition]
)
SELECT *
FROM y

您可能不需要这个功能。我做了以下只是为了更好地组织我的查询:

WITH y 
AS
(
  SELECT * 
  FROM MyTable
  WHERE [base_condition]
),
x
AS
(
  SELECT * 
  FROM y
  WHERE [something_else]
)
SELECT * 
FROM x

With不能嵌入工作，但它可以连续工作

;WITH A AS(
...
),
B AS(
...
)
SELECT *
FROM A
UNION ALL
SELECT *
FROM B

编辑 修正了语法…

还有，看看下面的例子

SQLFiddle演示

虽然不是严格嵌套的，但可以使用公共表表达式在后续查询中重用先前的查询。

要做到这一点，您正在寻找的语句的形式将是

WITH x AS 
(
    SELECT * FROM MyTable
), 
y AS 
(
    SELECT * FROM x
)
SELECT * FROM y

不支持嵌套的'With'，但你总是可以使用第二个With作为子查询，例如:

WITH A AS (
                --WITH B AS ( SELECT COUNT(1) AS _CT FROM C ) SELECT CASE _CT WHEN 1 THEN 1 ELSE 0 END FROM B --doesn't work
                SELECT CASE WHEN count = 1 THEN 1 ELSE 0 END AS CT FROM (SELECT COUNT(1) AS count FROM dual)
                union all
                select 100 AS CT from dual
           )
              select CT FROM A