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HierarchyID - Data Type - SQL Server

In SQL Server, the HierarchyID data type is a special data type used to manage hierarchical data structures. Introduced in SQL Server 2008, it provides an efficient and flexible way to store and navigate hierarchical data.

What is HierarchyID data type?

The HierarchyID data type is a binary data type used to represent hierarchical data structures. It consists of a variable-length byte array, with each byte representing a node in the hierarchy. The data type provides a set of built-in functions that allow you to perform common operations on hierarchical data, such as adding, deleting, and moving nodes.

The HierarchyID data type can represent any kind of hierarchical data structure, including trees, graphs, and organizational structures.

How to use HierarchyID data type?

To use HierarchyID data type in SQL Server, you first need to create a table with a column of type HierarchyID. For example, let's say you want to create a table to store an organizational chart. You can create a table like this:

CREATE TABLE Organization (

    NodeID HierarchyID PRIMARY KEY,

    NodeName VARCHAR(50)

);

You can then insert data into the table using the HierarchyID data type. For example, to insert the CEO of the organization, you can use the following statement:

INSERT INTO Organization (NodeID, NodeName) VALUES (HierarchyID::GetRoot(), 'CEO');

To insert a subordinate of the CEO, you can use the following statement:

INSERT INTO Organization (NodeID, NodeName) VALUES (HierarchyID::Parse('/1/'), 'Sales Manager');

This creates a new node with an ID of /1/1/, which represents a subordinate of the CEO.

HierarchyID data type provides several functions that allow you to navigate and manipulate hierarchical data. For example, to retrieve the path from the root node to a specific node, you can use the GetAncestor() function. The following statement retrieves the path from the root node to the Sales Manager node:

SELECT NodeName, NodeID.GetAncestor(1) as ManagerID

FROM Organization

WHERE NodeName = 'Sales Manager'

This returns the following result:

NodeName | ManagerID

--------------- |----------

Sales Manager  | /1/

Conclusion

The HierarchyID data type is a powerful tool for managing hierarchical data structures in SQL Server. It provides an efficient and flexible way to store and navigate hierarchical data. With the HierarchyID data type, you can easily represent complex hierarchical structures such as organizational charts, product categories, and more.

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