Question

Category (id, name,        parent_id);
          1   Electronics  NULL
          2   Computers    1
          3   Notebooks    2
          4   Desktops     2

Products (id, name,      category_id);
          1   NotebookX  3
          2   NotebookY  3
          3   NotebookZ  3
          4   DesktopX   2
          5   DesktopY   2

1-我想选择指定类别的父类别列表。

2-我想选择类别和子类别的产品列表。

Select category 1 should return 5 products. 
          1   NotebookX  3
          2   NotebookY  3
          3   NotebookZ  3
          4   DesktopX   2
          5   DesktopY   2
    Select category 2 should return 5 products. 
          1   NotebookX  3
          2   NotebookY  3
          3   NotebookZ  3
          4   DesktopX   2
          5   DesktopY   2
    Select category 3 should return 3 products. 
          1   NotebookX  3
          2   NotebookY  3
          3   NotebookZ  3
    Select category 4 should return 2 products.
          4   DesktopX   2
          5   DesktopY   2

我是sql递归查询的新手，因此无法创建。

WITH RECURSIVE graph AS (
    SELECT id, name
    FROM category
    WHERE parent_id IS NULL
    UNION ALL
    SELECT v.id, v.name
    FROM category as v
    JOIN graph r on v.parent_id = r.id
    ????????????
    ????????????
)
SELECT id, name FROM graph;

（我正在使用postgreql。但你可以编写任何数据库。）

Answer 1

试一试（ SQL Server 解决方案）：

DECLARE @category int = 3

;WITH rec AS (
SELECT *
FROM Category c
WHERE c.id = @category
UNION ALL
SELECT c.*
FROM rec r
INNER JOIN Category c
    ON c.parent_id = r.id
)

SELECT p.*
FROM Products p
INNER JOIN rec r
    ON r.id = p.category_id

首先我们得到一个我们选择的类别。比我们在递归部分中从Category所有孩子中选择。之后我们进入rec所有子类别。我们加入Products与rec的类别。

修改＃1

您可以将rec结果放入临时表中，然后使用它们：

SELECT * INTO #rec FROM rec SELECT p.* FROM Products p INNER JOIN #rec r ON r.id = p.category_id SELECT * FROM #rec DROP TABLE #rec

@category=3的输出：

id name category_id ----------- --------- ----------- 1 NotebookX 3 2 NotebookY 3 3 NotebookZ 3 (3 row(s) affected) id name parent_id ----------- ----------- ----------- 3 Notebooks 2 (1 row(s) affected)

修改＃2

获得后代：

DECLARE @category int = 2 ;WITH rec AS ( SELECT * FROM Category c WHERE c.id = @category UNION ALL SELECT c.* FROM rec r INNER JOIN Category c ON c.id = r.parent_id ) SELECT * FROM rec

输出：

id name parent_id 2 Computers 1 1 Electronics NULL

对于父母：

DECLARE @category int = 2 ;WITH rec AS ( SELECT * FROM Category c WHERE c.id = @category UNION ALL SELECT c.* FROM rec r INNER JOIN Category c ON c.parent_id = r.id )

输出：

id name parent_id 2 Computers 1 3 Notebooks 2 4 Desktops 2

具有父子项的分层SQL查询

1 个答案: