Sql 选择特定层次结构中的项目

我有一个文章类别表，如下所示：

---

作为第二个条款表：

| Id | CategoryId | Name
| 1  | 4          | Simple keyboard
| 2  | 5          | Simple mouse
| 3  | 6          | Simple nothing

Article.CategoryId->Category.Id

Category.ParentId->Category.Id

现在我需要选择所有属于计算机附件的文章。如何做到这一点？我尝试过做一些递归查询，但没有成功

预期结果是：

| 1 | Simple keyboard
| 2 | Simple mouse

---

由于他们的类别指向一个类别，该类别的父类别ID为2，我正在搜索该类别

，因此我认为您正在查找以下内容：

SELECT * FROM
Categories C
LEFT JOIN
Articles A
ON C.Id = A.CategoryId
WHERE C.Name = "Computer Accessories"

这将选择“计算机附件”作为名称-它有一个分配给它的ID，即2。通过加入，它将向您显示类别ID为2的所有文章。

尝试以下操作：

MS SQL Server 2012架构设置：

CREATE TABLE Category
(
  ID INT,
  ParentId INT,
  Name VARCHAR(255)
)

CREATE TABLE Article
(
  ID INT,
  CategoryId INT,
  Name VARCHAR(255)
)

INSERT INTO Category 
VALUES
  (6,1, 'Something Else'),
  (5,2, 'Mice'),
  (4,2, 'Keyboards'),
  (2,1,'Computer Accessories'),
  (1, 0, 'All')


INSERT INTO Article
VALUES
  (1,4,'Simple keyboard'),
  (2,5,'Simple mouse'),
  (3,6,'Simple nothing')

;WITH CTE
AS
(
  SELECT ID, ParentId, Name
  FROM Category
  WHERE Name = 'Computer Accessories'

  UNION ALL

  SELECT c1.ID, c1.ParentId, c1.Name
  FROM Category c1
  INNER JOIN CTE c2
    ON c1.ParentId = c2.Id
)
SELECT Article.Id, Article.Name
FROM CTE
INNER JOIN Article
  ON Article.CategoryId = CTE.Id

| ID |            NAME |
|----|-----------------|
|  1 | Simple keyboard |
|  2 |    Simple mouse |

查询1：

CREATE TABLE Category
(
  ID INT,
  ParentId INT,
  Name VARCHAR(255)
)

CREATE TABLE Article
(
  ID INT,
  CategoryId INT,
  Name VARCHAR(255)
)

INSERT INTO Category 
VALUES
  (6,1, 'Something Else'),
  (5,2, 'Mice'),
  (4,2, 'Keyboards'),
  (2,1,'Computer Accessories'),
  (1, 0, 'All')


INSERT INTO Article
VALUES
  (1,4,'Simple keyboard'),
  (2,5,'Simple mouse'),
  (3,6,'Simple nothing')

;WITH CTE
AS
(
  SELECT ID, ParentId, Name
  FROM Category
  WHERE Name = 'Computer Accessories'

  UNION ALL

  SELECT c1.ID, c1.ParentId, c1.Name
  FROM Category c1
  INNER JOIN CTE c2
    ON c1.ParentId = c2.Id
)
SELECT Article.Id, Article.Name
FROM CTE
INNER JOIN Article
  ON Article.CategoryId = CTE.Id

| ID |            NAME |
|----|-----------------|
|  1 | Simple keyboard |
|  2 |    Simple mouse |

：

CREATE TABLE Category
(
  ID INT,
  ParentId INT,
  Name VARCHAR(255)
)

CREATE TABLE Article
(
  ID INT,
  CategoryId INT,
  Name VARCHAR(255)
)

INSERT INTO Category 
VALUES
  (6,1, 'Something Else'),
  (5,2, 'Mice'),
  (4,2, 'Keyboards'),
  (2,1,'Computer Accessories'),
  (1, 0, 'All')


INSERT INTO Article
VALUES
  (1,4,'Simple keyboard'),
  (2,5,'Simple mouse'),
  (3,6,'Simple nothing')

;WITH CTE
AS
(
  SELECT ID, ParentId, Name
  FROM Category
  WHERE Name = 'Computer Accessories'

  UNION ALL

  SELECT c1.ID, c1.ParentId, c1.Name
  FROM Category c1
  INNER JOIN CTE c2
    ON c1.ParentId = c2.Id
)
SELECT Article.Id, Article.Name
FROM CTE
INNER JOIN Article
  ON Article.CategoryId = CTE.Id

| ID |            NAME |
|----|-----------------|
|  1 | Simple keyboard |
|  2 |    Simple mouse |

---

“我尝试过做一些递归查询”。。。你能把它寄出去吗？这两个表是如何链接的？你的层次结构有多深，预期的结果是什么？查询固定级别相对简单（最多5个级别-可以使用联接完成）；查询未知级别需要更多的努力（需要递归CTE或类似），谢谢，但这不是我需要的。我需要的文章有一个类别，这是另一个类别的孩子（ID 2）