首先,我非常熟悉LINQ查詢,但是在編寫直接SQL查詢時是一個完全新手。通過CTE通過LINQ進行Sql遞歸SelectMany
我希望能夠做到以下幾點:
- 對於任何給定的項目Id,遍歷它的子項,直到非常基礎的子項已經被選中。
每個項目都屬於一個容器,它具有指定的基礎容器Id(或父容器Id)(如果它是基本容器,則爲NULL)。一個容器只能有一個父容器,但它可以有多個子容器。
目前我一直在做類似如下:
using (MyEntities db = new MyEntities())
{
var theItem = db.Find(itemId);
var theContainer = theItem.Container.BaseContainer;
var theBaseItems = theItem.BaseItems.Where(bi => bi.ContainerId == theContainer.ContainerId).ToList();
while (theContainer.BaseContainerId != null)
{
theContainer = theContainer.BaseContainer;
theBaseItems = theBaseItems.SelectMany(bi => bi.BaseItems.Where(i => i.ContainerId == theContainer.ContainerId)).ToList();
}
}
這種運行良好和相當迅速,但是當數據筒是相當高的環比上漲,我注意到查詢到荒謬號該數據庫由SelectMany引起。例如,如果1000個項目屬於父容器中的100個項目,並且這100個項目屬於該容器父容器中的10個項目,並且最終那些屬於鏈接頂部的1個項目,則Select Many將運行10 + 100個查詢,每次取平均結果以檢索1000個基本項目 - 預計AFAIK。
因此,我懷疑(經過大量研究)Sql CTE可能是一個更好的選擇,不僅僅是輕輕點擊數據庫,但可能更快 - 這是一個糟糕的假設嗎?
然而,我仍然努力去處理CTE的語法,並希望有人能在我的問題上擺脫他們的智慧並幫助我。
重新創建方案
USE [TestDatabase]
GO
/****** Object: Table [dbo].[Containers] Script Date: 20/05/2013 14:17:20 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[Containers](
[ContainerId] [int] IDENTITY(1,1) NOT NULL,
[BaseContainerId] [int] NULL,
[Name] [nvarchar](50) NOT NULL,
CONSTRAINT [PK_Containers] PRIMARY KEY CLUSTERED
(
[ContainerId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
GO
/****** Object: Table [dbo].[ItemRelationships] Script Date: 20/05/2013 14:17:20 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[ItemRelationships](
[ChildItemId] [int] NOT NULL,
[ParentItemId] [int] NOT NULL,
CONSTRAINT [PK_ItemRelationships] PRIMARY KEY CLUSTERED
(
[ChildItemId] ASC,
[ParentItemId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
GO
/****** Object: Table [dbo].[Items] Script Date: 20/05/2013 14:17:20 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[Items](
[ItemId] [int] IDENTITY(1,1) NOT NULL,
[ContainerId] [int] NOT NULL,
[Name] [nvarchar](50) NOT NULL,
CONSTRAINT [PK_Items] PRIMARY KEY CLUSTERED
(
[ItemId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
GO
SET IDENTITY_INSERT [dbo].[Containers] ON
INSERT [dbo].[Containers] ([ContainerId], [BaseContainerId], [Name]) VALUES (1, NULL, N'Level 1')
INSERT [dbo].[Containers] ([ContainerId], [BaseContainerId], [Name]) VALUES (2, 1, N'Level 2')
INSERT [dbo].[Containers] ([ContainerId], [BaseContainerId], [Name]) VALUES (3, 1, N'Level 2b')
INSERT [dbo].[Containers] ([ContainerId], [BaseContainerId], [Name]) VALUES (4, 2, N'Level 3')
INSERT [dbo].[Containers] ([ContainerId], [BaseContainerId], [Name]) VALUES (5, NULL, N'TypeB')
SET IDENTITY_INSERT [dbo].[Containers] OFF
INSERT [dbo].[ItemRelationships] ([ChildItemId], [ParentItemId]) VALUES (1, 13)
INSERT [dbo].[ItemRelationships] ([ChildItemId], [ParentItemId]) VALUES (2, 13)
INSERT [dbo].[ItemRelationships] ([ChildItemId], [ParentItemId]) VALUES (3, 13)
INSERT [dbo].[ItemRelationships] ([ChildItemId], [ParentItemId]) VALUES (4, 14)
INSERT [dbo].[ItemRelationships] ([ChildItemId], [ParentItemId]) VALUES (5, 14)
INSERT [dbo].[ItemRelationships] ([ChildItemId], [ParentItemId]) VALUES (6, 14)
INSERT [dbo].[ItemRelationships] ([ChildItemId], [ParentItemId]) VALUES (7, 15)
INSERT [dbo].[ItemRelationships] ([ChildItemId], [ParentItemId]) VALUES (8, 15)
INSERT [dbo].[ItemRelationships] ([ChildItemId], [ParentItemId]) VALUES (9, 15)
INSERT [dbo].[ItemRelationships] ([ChildItemId], [ParentItemId]) VALUES (10, 16)
INSERT [dbo].[ItemRelationships] ([ChildItemId], [ParentItemId]) VALUES (11, 16)
INSERT [dbo].[ItemRelationships] ([ChildItemId], [ParentItemId]) VALUES (12, 16)
INSERT [dbo].[ItemRelationships] ([ChildItemId], [ParentItemId]) VALUES (13, 17)
INSERT [dbo].[ItemRelationships] ([ChildItemId], [ParentItemId]) VALUES (14, 17)
INSERT [dbo].[ItemRelationships] ([ChildItemId], [ParentItemId]) VALUES (15, 17)
INSERT [dbo].[ItemRelationships] ([ChildItemId], [ParentItemId]) VALUES (1007, 13)
INSERT [dbo].[ItemRelationships] ([ChildItemId], [ParentItemId]) VALUES (1008, 17)
SET IDENTITY_INSERT [dbo].[Items] ON
INSERT [dbo].[Items] ([ItemId], [ContainerId], [Name]) VALUES (1, 1, N'A')
INSERT [dbo].[Items] ([ItemId], [ContainerId], [Name]) VALUES (2, 1, N'B')
INSERT [dbo].[Items] ([ItemId], [ContainerId], [Name]) VALUES (3, 1, N'C')
INSERT [dbo].[Items] ([ItemId], [ContainerId], [Name]) VALUES (4, 1, N'D')
INSERT [dbo].[Items] ([ItemId], [ContainerId], [Name]) VALUES (5, 1, N'E')
INSERT [dbo].[Items] ([ItemId], [ContainerId], [Name]) VALUES (6, 1, N'F')
INSERT [dbo].[Items] ([ItemId], [ContainerId], [Name]) VALUES (7, 1, N'G')
INSERT [dbo].[Items] ([ItemId], [ContainerId], [Name]) VALUES (8, 1, N'H')
INSERT [dbo].[Items] ([ItemId], [ContainerId], [Name]) VALUES (9, 1, N'I')
INSERT [dbo].[Items] ([ItemId], [ContainerId], [Name]) VALUES (10, 1, N'J')
INSERT [dbo].[Items] ([ItemId], [ContainerId], [Name]) VALUES (11, 1, N'K')
INSERT [dbo].[Items] ([ItemId], [ContainerId], [Name]) VALUES (12, 1, N'L')
INSERT [dbo].[Items] ([ItemId], [ContainerId], [Name]) VALUES (13, 2, N'A2')
INSERT [dbo].[Items] ([ItemId], [ContainerId], [Name]) VALUES (14, 2, N'A2')
INSERT [dbo].[Items] ([ItemId], [ContainerId], [Name]) VALUES (15, 2, N'C2')
INSERT [dbo].[Items] ([ItemId], [ContainerId], [Name]) VALUES (16, 3, N'D2B')
INSERT [dbo].[Items] ([ItemId], [ContainerId], [Name]) VALUES (17, 4, N'A3')
INSERT [dbo].[Items] ([ItemId], [ContainerId], [Name]) VALUES (1007, 5, N'TypeB1')
INSERT [dbo].[Items] ([ItemId], [ContainerId], [Name]) VALUES (1008, 5, N'TypeB2')
SET IDENTITY_INSERT [dbo].[Items] OFF
ALTER TABLE [dbo].[Containers] WITH CHECK ADD CONSTRAINT [FK_Containers_Containers] FOREIGN KEY([BaseContainerId])
REFERENCES [dbo].[Containers] ([ContainerId])
GO
ALTER TABLE [dbo].[Containers] CHECK CONSTRAINT [FK_Containers_Containers]
GO
ALTER TABLE [dbo].[ItemRelationships] WITH CHECK ADD CONSTRAINT [FK_ItemRelationships_ChildItems] FOREIGN KEY([ParentItemId])
REFERENCES [dbo].[Items] ([ItemId])
GO
ALTER TABLE [dbo].[ItemRelationships] CHECK CONSTRAINT [FK_ItemRelationships_ChildItems]
GO
ALTER TABLE [dbo].[ItemRelationships] WITH CHECK ADD CONSTRAINT [FK_ItemRelationships_ParentItems] FOREIGN KEY([ChildItemId])
REFERENCES [dbo].[Items] ([ItemId])
GO
ALTER TABLE [dbo].[ItemRelationships] CHECK CONSTRAINT [FK_ItemRelationships_ParentItems]
GO
ALTER TABLE [dbo].[Items] WITH CHECK ADD CONSTRAINT [FK_Items_Containers] FOREIGN KEY([ContainerId])
REFERENCES [dbo].[Containers] ([ContainerId])
ON UPDATE CASCADE
ON DELETE CASCADE
GO
ALTER TABLE [dbo].[Items] CHECK CONSTRAINT [FK_Items_Containers]
GO
USE [master]
GO
ALTER DATABASE [TestDatabase] SET READ_WRITE
GO
下面的SQL查詢正確返回直接子項:
DECLARE @itemId BIGINT = 17;
SELECT
Items.ItemId
FROM
[TestDatabase].[dbo].[ItemRelationships]
INNER JOIN
[TestDatabase].[dbo].Items
ON
ItemRelationships.ChildItemId = Items.ItemId
INNER JOIN
[TestDatabase].[dbo].[Containers]
ON
Items.ContainerId = Containers.ContainerId
WHERE
ItemRelationships.ParentItemId = @itemId
AND
Items.ContainerId =
(
SELECT
BaseContainerId
FROM
[TestDatabase].[dbo].[Items]
INNER JOIN
[TestDatabase].[dbo].[Containers]
ON
Items.ContainerId = Containers.ContainerId
WHERE
Items.ItemId = @itemId
)
結果
項目編號17屬於容器4 。集裝箱4的基地集裝箱是集裝箱2,集裝箱2的基地容器是容器1,容器1的基本容器是NULL。
上述查詢返回容器2中的ItemIds 13,14和15(這是正確的)。但是,我需要此查詢來自動然後查找容器2的基本容器並獲取Item的基本項的所有ItemId 13,14和15(在這種情況下應該產生項目ID 1到9)。
注
- 作爲一個項可被附接(通過itemrelationships),以從容器無關項,當前項的檢查(或多個)容器的容器基必須存在。
- 如果傳遞的ItemId位於基本容器內,則查詢應簡單地返回傳遞的ItemId。
- CTE是首選,因爲結果實際上將用作針對另一個表的另一個查詢的一部分(但不在此問題的範圍之內)。
我希望有人能提前幫助和感謝您的努力。
非常有幫助,一個很好的開始 - 謝謝你。然而,我想確保的一些額外數據的測試在回報中避免了一些額外的記錄,這些記錄不應包含在最終結果中。我更新了數據庫創建腳本以提供這些記錄 - 實質上,應該不包含項目ID 1007和1008,因爲它們的容器不是項目標識17的容器層次結構的層次結構的一部分。註釋1007和1008鏈接到ID 13和17以模擬此。 –
標記爲答案,雖然沒有提供所需的確切結果,但爲CTE提供了寶貴的見解(簡單解釋)。謝謝。 –
@JonBellamy嗨,希望你能得到你需要的解決方案。對於不屬於子容器的子項目,請添加'WHERE c.ContainerId = i.ContainerId'到CTE的遞歸部分 –