SQL Server INNER JOIN with hierarchyid

Question

I have two tables, one table is the items container, which holds all data related to the products. The other table is for categories, in which the data is organised using hierarchies.
The goal of the query is to list items that match the category from the selected category down.

Example:

CatID: 3, Parent: Root, Name: Computers  
CatID: 4, Parent: 3, Name: Laptops  
CatID: 5, Parent: 3, Name: Monitors  
CatID: 6, Parent: 3, Name: Printers  
CatID: 7, Parent: 6, Name: Laser  
CatID: 8, Parent: 6, Name: Ink  
CatID: 9, Parent: 6, Name: Multifunction  
CatID: 10, Parent: 6, Name: Copier  

If the CatID selected is 3, all computer products will be displayed, but if the CatID 6 is selected, then only the printers will be displayed (items with CatID 7, 8, 9 and 10)

I'm rather new to hierarchy id and I have little idea on how to aproach this query.

Thanks to all who contribute.

Carlos

Schema of both tables The idea is to join mz_category to ic_item_cat, so a query could list all items for a given category, but also for all child categories. This is intended for a special "home made" treeview where all categories are displayed according to the hierarchy; when a user clicks a category, it displays all items that belong to that category and all items that belong to the child categories as well. Hope you get the idea.

/****** Object:  Table [dbo].[mz_category]    Script Date: 04/26/2012 19:14:34 ******/
SET ARITHABORT ON
GO
SET CONCAT_NULL_YIELDS_NULL ON
GO
SET ANSI_NULLS ON
GO
SET ANSI_PADDING ON
GO
SET ANSI_WARNINGS ON
GO
SET NUMERIC_ROUNDABORT OFF
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
SET ANSI_PADDING ON
GO
SET ARITHABORT ON
GO
/****** Categories Table ******/
CREATE TABLE [dbo].[mz_category](
    [CatNode] [hierarchyid] NOT NULL,
    [CatLevel]  AS ([CatNode].[GetLevel]()),
    [CatID] [int] NOT NULL,
    [CatName] [varchar](80) NOT NULL,
    [SectorId] [varchar](2) NULL,
    [CatIcon] [varchar](255) NULL,
    [oldCat] [varchar](8) NULL,
PRIMARY KEY CLUSTERED 
(
    [CatNode] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY],
UNIQUE NONCLUSTERED 
(
    [CatID] 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 ANSI_PADDING OFF
GO
/****** Object:  Table [dbo].[ic_item_cat]    Script Date: 04/26/2012 19:14:34 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
SET ANSI_PADDING ON
GO
/****** Items Table ******/
CREATE TABLE [dbo].[ic_item_cat](
    [item_code] [varchar](25) NOT NULL,
    [item_description] [varchar](80) NULL,
    [item_sector] [varchar](2) NULL,
    [item_line] [varchar](2) NULL,
    [item_reference] [varchar](50) NULL,
    [item_upcean] [varchar](50) NULL,
    [item_category] [int] NULL,
    [item_brand] [varchar](8) NULL,
    [item_cost] [decimal](12, 4) NULL,
    [item_price1] [decimal](12, 4) NULL,
    [item_price2] [decimal](12, 4) NULL,
    [item_price3] [decimal](12, 4) NULL,
    [item_webprice] [decimal](12, 4) NULL,
    [item_dprice1] [decimal](12, 4) NULL,
    [item_dprice2] [decimal](12, 4) NULL,
    [item_dprice3] [decimal](12, 4) NULL,
    [item_lastcost] [decimal](12, 4) NULL,
    [item_lastcostdate] [datetime] NULL,
    [item_lastqtyout] [decimal](12, 4) NULL,
    [item_lastqtyoutdate] [datetime] NULL,
    [item_lastqtyin] [decimal](12, 4) NULL,
    [item_lastqtyindate] [datetime] NULL,
    [item_additionaldesc] [varchar](max) NULL,
    [item_weight] [decimal](12, 4) NULL,
    [item_weight_measure] [varchar](2) NULL,
    [item_width] [decimal](12, 4) NULL,
    [item_width_measure] [varchar](2) NULL,
    [item_length] [decimal](12, 4) NULL,
    [item_length_measure] [varchar](2) NULL,
    [item_height] [decimal](12, 4) NULL,
    [item_height_measure] [varchar](2) NULL,
    [item_whpackdesc] [varchar](80) NULL,
    [item_salespackdesc] [varchar](80) NULL,
    [item_purchpackdesc] [varchar](80) NULL,
    [item_salespackconv] [decimal](12, 4) NULL,
    [item_purchpackconv] [decimal](12, 4) NULL,
    [item_warranty] [varchar](2) NULL,
    [item_delivtime] [varchar](2) NULL,
    [item_rating] [int] NULL,
    [item_vat] [varchar](2) NULL,
    [item_status] [int] NULL,
    [item_avgleadtime] [int] NULL,
    [web_flag] [bit] NULL,
    [partner_id] [varchar](25) NULL,
    [unique_id] [uniqueidentifier] NOT NULL
) ON [PRIMARY]
GO
SET ANSI_PADDING OFF
GO

Answer 1

Will something like this work?

DECLARE @CatNode hierarchyid;
SET @CatNode = (
    SELECT CatNode from mz_category
    WHERE CatID = @CatID
  );
SELECT * FROM Items
WHERE CatID IN (
  SELECT  CatID
  FROM    mz_category
  WHERE   CatNode.IsDescendantOf(@CatNode) = 1
);

Answer 2

You can use a CTE.

• Select the starting record(s)
• Get the children of these starting record(s) in the recursive part

SQL Statement

;WITH q AS (
  SELECT  CatID, Parent, Name
  FROM    YourTable
  WHERE   CatID = 3
  UNION ALL
  SELECT  t.CatID, t.Parent, t.Name
  FROM    q
          INNER JOIN YourTable t ON t.Parent = q.CatID
)
SELECT  *
FROM    q

Answer 3

DECLARE @CatID hierarchyid = '/6/';

WITH RootCategory AS (
    SELECT  CatID,
            Parent,
            Name
    FROM    Category
    WHERE   CatID = @CatID

    UNION ALL

    SELECT      C.CatID,
                C.Parent,
                C.Name
    FROM        Category C
    INNER JOIN  RootCategory R ON C.Parent = R.CatID
)
SELECT  *
FROM    RootCategory