The Art of SQL Server FILESTREAM - Red Gate Software

Chapter 11: FileTableUSE NorthPoleGOCREATE TABLE Hierarchy(path_locator HIERARCHYID NOT NULLPRIMARY KEY CLUSTERED ,parent_path_locator AS ( CASE WHEN path_locator.GetLevel() = 1THEN NULLELSE path_locator.GetAncestor(1)END )PERSISTEDFOREIGN KEY REFERENCES Hierarchy ( path_locator ) ,name NVARCHAR(255) NOT NULL)Listing 11-1:Create a sample hierarchy in SQL Server.The script creates a new table containing three fields with names also found inFileTables. The path_locator is the primary key, and the parent_path_locatoris a computed column. In addition, the parent_path_locator is also a foreign keywhich references the primary key of the same table. This is to ensure we cannot add achild for a non-existing parent. The name is the would-be name of the file or folderstored in the FileTable.Listing 11-2 demonstrates how a new row can be added to the Hierarchy table. It is upto the application to create the HIERARCHYID values. A HIERARCHYID can be writtenas a string representation, whereby each level in the hierarchy is separated using '/'.A HIERARCHYID value always starts and ends with a forward slash.INSERT INTO Hierarchy( path_locator, name )VALUES ( '/1/', '1.txt' )Listing 11-2:Adding a row to the hierarchy.393