T-SQL hierarchy - 使用查询获取面包屑

Question

我在数据库中保存了虚拟文件夹结构，我想将面包屑从当前文件夹获取到根目录。数据可以不排序（但更好的是排序），我只想要当前文件夹的父文件夹。

table定义是：

DECLARE Folders TABLE (
    FOL_PK INT IDENTITY(1,1) NOT NULL,
    FOL_Name VARCHAR(200) NOT NULL,
    FOL_FOL_FK INT NULL -- Foreign key to parent
)

这是我的解决方案：

DECLARE @FOL_PK INT = 5 -- Current folder PK

DECLARE @breadcrumbs TABLE (
    FOL_PK INT NOT NULL,
    FOL_Name VARCHAR(200) NOT NULL,
    FOL_FOL_FK INT NULL
)

DECLARE @isRoot BIT = 0
       ,@currentFolderPK INT
       ,@parentFK INT

-- Get current and parent folder PK
SELECT
    @currentFolderPK = FOL_PK
FROM
    Folder
WHERE
    FOL_PK = @FOL_PK

-- Breadcrumb
WHILE (@isRoot = 0)
BEGIN
    -- Save to breadcrumb
    INSERT INTO @breadcrumbs
        SELECT
            FOL_PK,
            FOL_Name,
            FOL_FOL_FK
        FROM
            Folder
        WHERE
            FOL_PK = @currentFolderPK

    -- Set parent as current
    SET @currentFolderPK =
    (
        SELECT
            FOL_FOL_FK
        FROM
            Folder
        WHERE
            FOL_PK = @currentFolderPK
    )

    -- Set flag for loop
    SET @isRoot = CASE 
                     WHEN ISNULL(@currentFolderPK, 0) = 0 THEN 1 
                     ELSE 0 
                  END
END

-- Return breadcrumbs
SELECT
    FOL_PK AS PK,
    FOL_Name AS Name,
    FOL_FOL_FK AS ParentFK
FROM
    @breadcrumbs

问题是我对这个循环不太满意table。有没有其他复杂的解决方案如何做到这一点？

Answer 1

尝试使用递归通用Table表达式 (CTE):

SQL Fiddle

MS SQL Server 2008 架构设置:

CREATE TABLE [Folders](
    [FOL_PK] [int] IDENTITY(1,1) NOT NULL,
    [FOL_Name] [varchar](200) NOT NULL,
    [FOL_FOL_FK] [int] NULL,
 CONSTRAINT [PK__Folders__FOL_PK] PRIMARY KEY CLUSTERED 
(
    [FOL_PK] ASC
))

ALTER TABLE [dbo].[Folders]  
  WITH CHECK ADD  CONSTRAINT [FK_Folders_Folders] FOREIGN KEY([FOL_FOL_FK])
REFERENCES [dbo].[Folders] ([FOL_PK])

ALTER TABLE [dbo].[Folders] CHECK CONSTRAINT [FK_Folders_Folders]



INSERT INTO Folders(FOL_Name, FOL_FOL_FK)
VALUES ('Level 1', NULL),
       ('Level 1.1', 1),
       ('Level 1.2', 1),
       ('Level 1.3', 1),
       ('Level 1.2.1', 3),
       ('Level 1.2.2', 3),
       ('Level 1.2.3', 3),
       ('Level 1.2.2.1', 6),
       ('Level 1.2.2.2', 6),
       ('Level 1.2.2.3', 6),
       ('Level 1.3.1', 4),
       ('Level 1.3.2', 4)

查询 1:

DECLARE @FolderId Int = 9

;WITH CTE
AS
(
    SELECT FOL_PK AS PK, FOL_NAME As Name, FOL_FOL_FK AS ParentFK
    FROM Folders
    WHERE FOL_PK = @FolderId
    UNION ALL
    SELECT F.FOL_PK AS PK, F.FOL_NAME AS Name, F.FOL_FOL_FK AS ParentFK
    FROM Folders F
    INNER JOIN CTE C
        ON C.ParentFK = F.FOL_PK

)
SELECT *
FROM CTE

Results:

| PK |          Name | ParentFK |
|----|---------------|----------|
|  9 | Level 1.2.2.2 |        6 |
|  6 |   Level 1.2.2 |        3 |
|  3 |     Level 1.2 |        1 |
|  1 |       Level 1 |   (null) |

T-SQL hierarchy - 使用查询获取面包屑

T-SQL hierarchy - get breadcrumbs using query

sql-server

tsql

hierarchical-data