Question

我正在尝试使用递归更新表（具有树结构）。我使用下面的代码（唯一的区别是不使用更新部分以及CTE的最后选择查询而不是原始表）来显示任何给定节点的子树，在这种情况下它是硬编码的＆＃ 39; G＆＃39 ;.

我现在需要更新子树的值但是使用下面的代码我遇到了一个错误，导致无法识别。更新查询附近发生systax错误。

WITH RECURSIVE ph AS
(
    -- Anchor
    SELECT attr1, attr3, attr4
    FROM entity
    WHERE attr3 = 'G'

    UNION ALL

    -- Recursive Member
    SELECT entity.attr1, entity.attr3, entity.attr4
    FROM entity, ph     
    WHERE ph.attr1 = entity.attr3

    -- update original table (not the cte)
    UPDATE entity
    SET attr4 = entity.attr4 * 1.1
    FROM ph
    WHERE ph.attr1 = entity.attr3;
)

    --see result with updated values
    Select * from entity;

解决了以下问题。

WITH RECURSIVE ph AS
(
    -- Anchor
    SELECT attr1, attr3, attr4
    FROM entity
    WHERE attr3 = 'E'

    UNION ALL

    -- Recursive Member
    SELECT entity.attr1, entity.attr3, entity.attr4
    FROM entity, ph     
    WHERE ph.attr1 = entity.attr3
)

    --see result with updated values
    UPDATE entity
    SET attr4 = attr4 * 100
    WHERE attr1 IN (SELECT attr1 FROM ph)
    RETURNING *;

Answer 1

UPDATE不能成为递归 SELECT 的一部分。您需要使用SELECT的结果进行UPDATE：

WITH RECURSIVE ph AS
(
    -- Anchor
    SELECT attr1, attr3, attr4
    FROM entity
    WHERE attr3 = 'G'

    UNION ALL

    -- Recursive Member
    SELECT entity.attr1, entity.attr3, entity.attr4
    FROM entity, ph     
    WHERE ph.attr1 = entity.attr3

)
    -- update original table (not the cte)
    UPDATE entity
    SET attr4 = entity.attr4 * 1.1
    FROM ph
    WHERE ph.attr1 = entity.attr3;

--see result with updated values
Select * from entity;

在Postgres中递归更新表

1 个答案: