在PostgreSQL视图中自加入

Question

我正在尝试创建可以从加入来源积累所有必要数据的视图：

CREATE OR REPLACE VIEW dir AS
SELECT
    dir_data.id,
    dir_data.parent_id,
    dir_data.name,
    (owner.*)::owner, -- owner_id
FROM
    dir_data
    LEFT JOIN owner ON owner.id = dir_data.owner_id

例如，这允许以简单的方式选择所有者的数据：

SELECT
    id,
    name,
    (owner).id AS owner_id,
    (owner).name AS owner_name,
    ((owner).company).name AS owner_company
FROM
    dir
WHERE
    id = 7

问题是我需要与视图进行自我加入 dir （正在创建的VEW）转换 parent_id 以相似的方式进行字段。 PostgreSQL似乎不喜欢它，它说 relation "dir" does not exist.

有提示吗？

---

回答Marcelo Cantos评论：

CREATE OR REPLACE VIEW dir AS
SELECT
    ...
FROM
    dir_data
    LEFT JOIN owner ON owner.id = dir_data.owner_id -- "standard" join
    LEFT JOIN dir AS parent_dir ON parent_dir.id = dir_data.parent_id -- self-join, does not work

Answer 1

您无法创建递归视图，但是在最新的Postgres中，您可以进行递归查询： http://www.postgresql.org/docs/8.4/static/queries-with.html

Answer 2

WITH    RECURSIVE dir AS
        (
        SELECT  dir_data.id,
                dir_data.parent_id,
                dir_data.name,
                owner
        FROM    dir_data
        LEFT JOIN
                owner
        ON      owner.id = dir_data.owner_id
        WHERE   dir_data.id = 7
        UNION ALL
        SELECT  dir_data.id,
                dir_data.parent_id,
                dir_data.name,
                owner
        FROM    dir
        JOIN    dir_data
        ON      dir_data.id = dir.parent_id
        LEFT JOIN
                owner
        ON      owner.id = dir_data.owner_id
        )
SELECT  *
FROM    dir