PostgreSQL分層，分類樹

Question

ENV：postgresql-8.4

我試圖建立一個類別樹。基本上我期待的最終輸出是：

 
categoryName 
categoryPath 
leafcategory 

：

 
Digital Camera 
Electronics ::: Digital Camera 
true 

表結構是

 
CREATE TABLE categories (
    id SERIAL PRIMARY KEY, 
    categoryid bigint, 
    categoryparentid bigint, 
    categoryname text, 
    status integer DEFAULT 0, 
    lang text, 
    eysiteid text, 
    country text, 
    tempid text, 
    leafcategory boolean 
);
 

到目前爲止，我已經得到了這一點，但不工作。任何幫助將高度讚賞：從數據庫

 
cat=> select * from categories; 
    id | categoryid | categoryparentid |   categoryname   | status | lang | eysiteid | country | tempid | leafcategory 
-------+------------+------------------+--------------------------------+--------+------+------------+---------+--------+-------------- 
    1 |   -1 |    0 | Root       |  1 | en | 0   | us  |  | f 
    2 |  20081 |    -1 | Antiques      |  1 | en | 0   | us  |  | f 
    17 |  1217 |   20081 | Primitives      |  0 | en | 0   | us  |  | t 
    23 |  22608 |   20081 | Reproduction Antiques   |  0 | en | 0   | us  |  | t 
    24 |   12 |   20081 | Other       |  0 | en | 0   | us  |  | t 
    25 |  550 |    -1 | Art       |  1 | en | 0   | us  |  | f 
    29 |  2984 |    -1 | Baby       |  1 | en | 0   | us  |  | f 

Answer 1

看來你加入了錯誤的領域

 
WITH RECURSIVE tree (CategoryID, CategoryParentID, CategoryName, category_tree, depth) 
AS ( 
    SELECT 
     CategoryID, 
     CategoryParentID, 
     CategoryName, 
     CategoryName AS category_tree, 
     0 AS depth 
    FROM categories 
    WHERE CategoryParentID IS NULL 
UNION ALL 
    SELECT 
     c.CategoryID, 
     c.CategoryParentID, 
     c.CategoryName, 
     tree.category_tree || '/' || c.CategoryName AS category_tree, 
     depth+1 AS depth 
    FROM tree 
     JOIN categories c ON (tree.category_tree = c.CategoryParentID) 
) 
SELECT * FROM tree ORDER BY category_tree; 

樣品。

-- create some test data 
DROP SCHEMA tmp CASCADE; 
CREATE SCHEMA tmp ; 
SET search_path=tmp; 

CREATE TABLE categories 
    -- (id SERIAL PRIMARY KEY 
    (categoryid SERIAL PRIMARY KEY 
    , categoryparentid bigint REFERENCES categories(categoryid) 
    , categoryname text 
    -- , status integer DEFAULT 0 
    -- , lang text 
    -- , ebaysiteid text 
    -- , country text 
    -- , tempid text 
    -- , leafcategory boolean 
     ); 
INSERT INTO categories(categoryid,categoryparentid) SELECT gs, 1+(gs/6)::integer 
FROM generate_series(1,50) gs; 

UPDATE categories SET categoryname = 'Name_' || categoryid::text; 
UPDATE categories SET categoryparentid = NULL WHERE categoryparentid <= 0; 
UPDATE categories SET categoryparentid = NULL WHERE categoryparentid >= categoryid; 


WITH RECURSIVE tree (categoryid, categoryparentid, categoryname, category_tree, depth) 
AS (
    SELECT 
     categoryid 
     , categoryparentid 
     , categoryname 
     , categoryname AS category_tree 
     , 0 AS depth 
    FROM categories 
    WHERE categoryparentid IS NULL 
UNION ALL 
    SELECT 
     c.categoryid 
     , c.categoryparentid 
     , c.categoryname 
     , tree.category_tree || '/' || c.categoryname AS category_tree 
     , depth+1 AS depth 
    FROM tree 
     JOIN categories c ON tree.categoryid = c.categoryparentid 
    ) 
SELECT * FROM tree ORDER BY category_tree; 

編輯：其他（ 「非功能」）符號遞歸似乎更好的工作：

WITH RECURSIVE tree AS (
    SELECT 
     categoryparentid AS parent 
     , categoryid AS self 
     , categoryname AS treepath 
     , 0 AS depth 
    FROM categories 
    WHERE categoryparentid IS NULL 
UNION ALL 
    SELECT 
     c.categoryparentid AS parent 
     , c.categoryid AS self 
     , t.treepath || '/' || c.categoryname AS treepath 
     , depth+1 AS depth 
    FROM categories c 
    JOIN tree t ON t.self = c.categoryparentid 
    ) 
SELECT * FROM tree ORDER BY parent,self 
    ; 

更新：在原來的查詢，就應該更換

WHERE CategoryParentID IS NULL 

通過：

WHERE CategoryParentID = 0 

或m aybe甚至：

WHERE COALESCE(CategoryParentID, 0) = 0 

Answer 2

看看this gist它或多或少是你想要做的。在你的情況下，我最好用LTree materialized path Postgresql's extension。