Question

我正在尝试创建可以累积所有联接来源所需数据的视图：

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

问题是我需要使用视图dir（正在创建的vew）进行自联接，以类似的方式转换parent_id字段。 PostgreSQL似乎不喜欢它，它说relation "dir" does not exist。

任何提示？

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

在PostgreSQL视图中自我加入

2 个答案: