在PostgreSQL中使用REC里面的WITH [复制]

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参见英文答案 > Issue with recursive CTE in PostgreSQL                                    1个
>             Multiple CTE in single query                                    2个
在Postgresql中,另一个WITH可以使用WITH,例如：

WITH num AS (
    VALUES (50)
),num2 AS (
    SELECT column1 * 2 AS value FROM num
)
SELECT value FROM num2;

还有RECURSIVE WITHs,可以这样做：

WITH RECURSIVE t(n) AS (
    VALUES (1)
  UNION ALL
    SELECT n+1 FROM t WHERE n < 100
)
SELECT sum(n) FROM t;

但到目前为止,我还没有找到一种方法让RECURSIVE WITH使用之前的WITH.我认为它应该是这样的：

WITH num AS (
    VALUES (50)
),num2 AS (
    SELECT column1 * 2 AS value FROM num
),RECURSIVE  t(n) AS (
        VALUES (1)
    UNION ALL
        SELECT n+1 FROM t WHERE n < (SELECT * FROM num2)
)
SELECT sum(n) FROM t;

但这不起作用.有没有办法做到这一点？如果是这样,怎么样？

解决方法

从WITH RECURSIVE开始.您仍然可以在递归部分之前挤入“常规”CTE：

WITH RECURSIVE
   num  AS (VALUES (50)),num2 AS (SELECT column1 * 2 AS value FROM num),t(n) AS (
      VALUES (1)
      UNION ALL
      SELECT n+1 FROM t WHERE n < (SELECT * FROM num2)
   )
SELECT sum(n) FROM t;

-> SQLfiddle demo.