Article
02/09/2012

SqlHierarchyId Structure

The SqlHierarchyId type represents a position in a hierarchical structure, specifying depth and breadth.

Namespace: Microsoft.SqlServer.Types
Assembly: Microsoft.SqlServer.Types (in Microsoft.SqlServer.Types.dll)

Syntax

'Declaration
<SqlUserDefinedTypeAttribute(Format.UserDefined, IsByteOrdered := True,  _
    MaxByteSize := , Name := "SqlHierarchyId")> _
<CLSCompliantAttribute(True)> _
Public Structure SqlHierarchyId _
    Implements IBinarySerialize, INullable, IComparable
'Usage
Dim instance As SqlHierarchyId

[SqlUserDefinedTypeAttribute(Format.UserDefined, IsByteOrdered = true, 
    MaxByteSize = , Name = "SqlHierarchyId")]
[CLSCompliantAttribute(true)]
public struct SqlHierarchyId : IBinarySerialize, 
    INullable, IComparable

[SqlUserDefinedTypeAttribute(Format::UserDefined, IsByteOrdered = true, 
    MaxByteSize = , Name = L"SqlHierarchyId")]
[CLSCompliantAttribute(true)]
public value class SqlHierarchyId : IBinarySerialize, 
    INullable, IComparable

[<SealedAttribute>]
[<SqlUserDefinedTypeAttribute(Format.UserDefined, IsByteOrdered = true, 
    MaxByteSize = , Name = "SqlHierarchyId")>]
[<CLSCompliantAttribute(true)>]
type SqlHierarchyId =  
    struct
        interface IBinarySerialize
        interface INullable
        interface IComparable
    end

JScript suports the use of structures, but not the declaration of new ones.

The SqlHierarchyId type exposes the following members.

Properties

	Name	Description
	IsNull	Gets a value indicating whether the SqlHierarchyId is nulla null reference (Nothing in Visual Basic).
	Null	Gets a SqlHierarchyId with a hierarchy identification of nulla null reference (Nothing in Visual Basic).

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Methods

	Name	Description
	CompareTo(Object)	Returns a value indicating the results of a comparison between a SqlHierarchyId and an object.
	CompareTo(SqlHierarchyId)	Returns a value indicating the results of a comparison between two SqlHierarchyId nodes.
	Equals	Evaluates whether SqlHierarchyId and obj are equal. (Overrides ValueType.Equals(Object).)
	Finalize	(Inherited from Object.)
	GetAncestor	Retrieves the SqlHierarchyId node n levels up the hierarchical tree.
	GetDescendant	Gets the value of a descendant SqlHierarchyId node that is greater than child1 and less than child2.
	GetHashCode	Gets a hash of the path from the root node of the hierarchy tree to the SqlHierarchyId node. (Overrides ValueType.GetHashCode().)
	GetLevel	Gets a value indicating the level of the SqlHierarchyId node in the hierarchical tree.
	GetReparentedValue	Gets a value representing the location of a new SqlHierarchyId node that has a path from newRoot equal to the path from oldRoot to this, effectively moving this to the new location.
	GetRoot	Gets a value representing the root SqlHierarchyId node of the hierarchy.
	GetType	(Inherited from Object.)
	IsDescendantOf	Gets a value indicating whether the SqlHierarchyId node is the descendant of the parent.
	MemberwiseClone	(Inherited from Object.)
	Parse	Converts the canonical string representation of a SqlHierarchyId node to a SqlHierarchyId value.
	Read	Reads from a specified binary reader into a SqlHierarchyId.
	ToString	Returns the canonical string representation of a SqlHierarchyId node from a SqlHierarchyId value. (Overrides ValueType.ToString().)
	Write	Writes a SqlHierarchyId to a specified binary writer.

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Operators

	Name	Description
	Equality	Evaluates whether two SqlHierarchyId nodes are equal.
	GreaterThan	Evaluates whether one specified SqlHierarchyId node is greater than another.
	GreaterThanOrEqual	Evaluates whether one specified SqlHierarchyId node is greater than or equal to another.
	Inequality	Evaluates whether two SqlHierarchyId nodes are unequal.
	LessThan	Evaluates whether one specified SqlHierarchyId node is less than another.
	LessThanOrEqual	Evaluates whether one specified SqlHierarchyId node is less than or equal to another.

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Remarks

This type provides the following benefits for storing hierarchical information:

Very compact data storage.
Depth-first comparison. Indexes on this type are in depth-first order, and nodes close to each other in a depth-first traversal are stored near each other.
Support for arbitrary insertions and deletions.
A limitation of this type is that a single instance of the hierarchy data type can be no larger than 892 bytes. Hierarchies that possess too many levels to fit within this limitation must use a different data type.

The HierarchyId type is available to CLR clients as the SqlHierarchyId data type.

Examples

DECLARE @employee hierarchyid
SELECT @employee = OrgNode FROM HumanResources.EmployeeDemo
  WHERE LoginID = 'adventure-works\dylan0'

SELECT * FROM HumanResources.EmployeeDemo
WHERE @employee.IsDescendantOf(OrgNode) = 1

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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