PostgreSQL中

Question

在PostgreSQL使用使用RECURSIVE WITH的内侧，带可以由另一个与其一起使用，例如：

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

再就是RECURSIVE WITHs，其可以像这样进行：

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

但是到目前为止，我还没有找到使用先前WITH的RECURSIVE WITH的方法。我会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。那么有没有办法做到这一点？如果是这样，怎么样？

Answer 1

开始于WITH RECURSIVE。您仍然可以递归部分之前挤进“正规”的热膨胀系数：

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.