Question

我将数据存储在层次结构中。我需要一个可以向我显示层次结构的查询。因此，一张床位于一个小区中，位于一个楼层，位于一个大楼内。

我需要做的是根据给定的位置ID显示整个位置。

一个人可能在床上，在牢房里，在地板上......或在建筑物内。我有位置ID。我需要做的是显示该人的位置。

例如，此人在Cell中，在数据库中，可能是ID 350.我需要能够构建他的位置字符串，以显示如下内容：

2号楼1号楼1号楼

或者，用户在某处的Building 1中，因此Building 1的ID可能是3.所以我需要显示Building 1，Block 2。

这两张桌子。一个用于保存位置，另一个用于查看类型。

有没有一种有效的方法来查询这类数据？我可能还有另外一个要求显示数百人的位置，因此查询基本上会运行很多次。

我尝试过递归CTE，但我发现的例子只能处理一个级别（我想？）。

也许返回表的函数是最好的方法？但问题是 - 取决于＆＃39; Level＆＃39;你开始时，可能会有更少的列。

我需要一种方法来解决这个问题。

CREATE TABLE [dbo].[Location]
(
 [ID] Int IDENTITY(1,1) NOT NULL,
 [ParentID] Int NULL,
 [LocationTypeID] Int NOT NULL,
 [Description] Varchar(100) NOT NULL
)
ON [PRIMARY]
go

-- Add keys for table dbo.Location

ALTER TABLE [dbo].[Location] ADD CONSTRAINT [pk_location] PRIMARY KEY ([ID])
 ON [PRIMARY]
go


CREATE TABLE [LocationType]
(
 [ID] Int IDENTITY(1,1) NOT NULL,
 [Description] Varchar(100) NOT NULL
)
ON [PRIMARY]
go

ALTER TABLE [LocationType] ADD CONSTRAINT [pk_location] PRIMARY KEY ([ID])
 ON [PRIMARY]
go

现在我们将填充一些查找数据：

INSERT INTO LocationType (Description) VALUES ('Bed')
INSERT INTO LocationType (Description) VALUES ('Cell')
INSERT INTO LocationType (Description) VALUES ('Floor')
INSERT INTO LocationType (Description) VALUES ('Building')
INSERT INTO LocationType (Description) VALUES ('Block')

然后创建一些位置数据。

-- Create the root items, which are the blocks. We'll have 2.

INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (NULL, 5, 'Block A') -- 1
INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (NULL, 5, 'Block B') -- 2

-- Now add 3 buildings per block.

-- Block A
INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (1, 4, 'Building 1') -- 3
INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (1, 4, 'Building 2') -- 4
INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (1, 4, 'Building 3') -- 5


-- Block B
INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (2, 4, 'Building 1') -- 6
INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (2, 4, 'Building 2') -- 7
INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (2, 4, 'Building 3') -- 8

-- Now add two floors per building.

-- Building 1 Block A
INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (3, 3, '1st Floor') -- 9
INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (3, 3, '2nd Floor') -- 10

-- Building 2 Block A
INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (4, 3, '1st Floor') -- 11
INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (4, 3, '2nd Floor') -- 12

-- Building 3 Block A
INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (5, 3, '1st Floor') -- 13
INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (5, 3, '2nd Floor') -- 14




-- Building 1 Block B
INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (6, 3, '1st Floor') -- 15
INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (6, 3, '2nd Floor') -- 16

-- Building 2 Block B
INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (7, 3, '1st Floor') -- 17
INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (7, 3, '2nd Floor') -- 18

-- Building 3 Block B
INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (8, 3, '1st Floor') -- 19
INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (8, 3, '2nd Floor') -- 20

- 现在，只需一个光标来填充细胞和床。

DECLARE @ThisID INT
DECLARE @Cntr INT  = 0

DECLARE mycursor CURSOR FOR
SELECT id from Location where LocationTypeID = 3

OPEN mycursor

FETCH NEXT FROM mycursor
INTO @ThisID

WHILE @@FETCH_STATUS = 0
BEGIN

    SET @Cntr = 1
    WHILE(@Cntr < 20)
    BEGIN
        INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (@ThisID, 4, 'Cell ' + CAST(@Cntr AS VARCHAR))  
        SET @Cntr = @Cntr + 1
    END

    FETCH NEXT FROM mycursor
    INTO @ThisID

END

CLOSE mycursor
DEALLOCATE mycursor


-- Now add two beds per cell
DECLARE my_cursor CURSOR FOR
SELECT id from Location where LocationTypeID = 4

OPEN my_cursor

FETCH NEXT FROM my_cursor
INTO @ThisID

WHILE @@FETCH_STATUS = 0
BEGIN

    INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (@ThisID, 5, 'Bed 1')   
    INSERT INTO Location (ParentId, LocationTypeID, Description) VALUES (@ThisID, 5, 'Bed 2')   

    FETCH NEXT FROM my_cursor
    INTO @ThisID

END

CLOSE my_cursor
DEALLOCATE my_cursor

Answer 1

这是一个递归的CTE解决方案：

WITH rCTE AS(
    SELECT
        l.*, CAST(l.Description AS VARCHAR(MAX)) AS FullLoc
    FROM Location l
    INNER JOIN LocationType  lt ON lt.ID = l.LocationTypeID
    WHERE l.ParentID IS NULL

    UNION ALL

    SELECT
        l.*, CAST(l.Description AS VARCHAR(MAX)) + ', ' + r.FullLoc
    FROM Location l
    INNER JOIN LocationType  lt ON lt.ID = l.LocationTypeID
    INNER JOIN rCTE r
        ON r.ID = l.ParentID
)
SELECT
    ID, FullLoc
FROM rCTE 
WHERE ID IN(21, 111, 190)
ORDER BY ID
OPTION (MAXRECURSION 0)

Answer 2

解决这个问题的最简单方法是使用LEFT JOIN ..但是当层次结构级别未知或可能变得非常深时它变得棘手..如果层次结构级别可以预先确定，那么这个SQL代码将起作用

SELECT
    L0.ID,
    L0.[Description] + 
    ISNULL(', ' + L1.[Description], '')  +
    ISNULL(', ' + L2.[Description], '')  +
    ISNULL(', ' + L3.[Description], '')  +
    ISNULL(', ' + L4.[Description], '')  +
    ISNULL(', ' + L5.[Description], '') FullLocation
FROM Location L0
    LEFT JOIN Location L1 ON L1.ID = L0.[ParentID]
    LEFT JOIN Location L2 ON L2.ID = L1.[ParentID]
    LEFT JOIN Location L3 ON L3.ID = L2.[ParentID]
    LEFT JOIN Location L4 ON L4.ID = L3.[ParentID]
    LEFT JOIN Location L5 ON L5.ID = L4.[ParentID]
WHERE
    L0.ID IN (21, 111, 190)

结果

╔═════╦═════════════════════════════════════════╗
║ ID  ║              FullLocation               ║
╠═════╬═════════════════════════════════════════╣
║  21 ║ Cell 1, 1st Floor, Building 1, Block A  ║
║ 111 ║ Cell 15, 1st Floor, Building 3, Block A ║
║ 190 ║ Cell 18, 1st Floor, Building 2, Block B ║
╚═════╩═════════════════════════════════════════╝

对heirarchal数据的递归查询

2 个答案: