<分区>
在 PostgreSQL 中,一个 WITH 可以被另一个 WITH 使用,例如:
WITH num AS (
VALUES (50)
), num2 AS (
SELECT column1 * 2 AS value FROM num
)
SELECT value FROM num2;
然后是 RECURSIVE WITH,可以像这样完成:
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,我还没有找到让递归 WITH 使用前一个 WITH 的方法。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;
但这行不通。那么有没有办法做到这一点?如果是,怎么办?