Bevar forældre-barn-relationer, når du kopierer hierarkiske data

En CTE fungerer fint med MERGE , men er problematisk i SQL Server 2005. Beklager den vildledende kommentar tidligere.

Det følgende viser, hvordan man kloner et projekt (med flere træer) og retter op på afstamningen for at adskille den nye skov fra den gamle. Bemærk, at det ikke afhænger af nogen bestemt arrangement af id'er, f.eks. de behøver ikke at være tætte, monotont stigende, ... .

-- Sample data.
declare @Projects as Table
  ( Id Int Identity, ProjectId Int, Value VarChar(16), ParentId Int Null );
insert into @Projects ( ProjectId, Value, ParentId ) values
  ( 611, 'Animal', 0 ),
  ( 611, 'Frog', 1 ),
  ( 611, 'Cow', 1 ),
  ( 611, 'Jersey Cow', 3 ),
  ( 611, 'Plant', 0 ),
  ( 611, 'Tree', 5 ),
  ( 611, 'Oak', 6 );
-- Display the raw data.
select * from @Projects;

-- Display the forest.
with IndentedProjects ( Id, ProjectId, Value, ParentId, Level, Path ) as
  ( -- Start with the top level rows.
  select Id, ProjectId, Value, ParentId, 0, Convert( VarChar(1024), Right( '000' + Convert( VarChar(4), Id ), 4 ) )
    from @Projects
    where ParentId = 0
  union all
  -- Add the children one level at a time.
  select P.Id, P.ProjectId, P.Value, P.ParentId, IP.Level + 1, Convert( VarChar(1024), IP.Path + '<' + Right( '000' + Convert( VarChar(4), P.Id ), 4 ) )
    from IndentedProjects as IP inner join
      @Projects as P on P.ParentId = IP.Id
  )
  select Space( Level * 2 ) + Value as [IndentedValue], Id, ProjectId, Value, ParentId, Level, Path
    from IndentedProjects
    order by Path;

-- Clone the project.
declare @OldProjectId as Int = 611;
declare @NewProjectId as Int = 42;
declare @Fixups as Table ( OldId Int, [NewId] Int );
begin transaction -- With suitable isolation since the hierarchy will be invalid until we apply the fixups!
insert into @Projects
  output Inserted.ParentId, Inserted.Id
    into @Fixups
  select @NewProjectId, Value, Id -- Note that we save the old Id in the new ParentId.
    from @Projects as P
    where ProjectId = @OldProjectId;
-- Apply the fixups.
update PNew
  set ParentId = IsNull( FNew.[NewId], 0 )
  -- Output the fixups just to show what is going on.
  output Deleted.Id, Deleted.ParentId as [ParentIdBeforeFixup], Inserted.ParentId as [ParentIdAfterFixup]
  from @Fixups as F inner join
    @Projects as PNew on PNew.Id = F.[NewId] inner join -- Rows we need to fix.
    @Fixups as FOld on FOld.OldId = PNew.ParentId inner join
    @Projects as POld on POld.Id = FOld.OldId left outer join
    @Fixups as FNew on FNew.OldId = POld.ParentId;
commit transaction;

-- Display the forest.
with IndentedProjects ( Id, ProjectId, Value, ParentId, Level, Path ) as
  ( -- Start with the top level rows.
  select Id, ProjectId, Value, ParentId, 0, Convert( VarChar(1024), Right( '000' + Convert( VarChar(4), Id ), 4 ) )
    from @Projects
    where ParentId =0
  union all
  -- Add the children one level at a time.
  select P.Id, P.ProjectId, P.Value, P.ParentId, IP.Level + 1, Convert( VarChar(1024), IP.Path + '<' + Right( '000' + Convert( VarChar(4), P.Id ), 4 ) )
    from IndentedProjects as IP inner join
      @Projects as P on P.ParentId = IP.Id
  )
  select Space( Level * 2 ) + Value as [IndentedValue], Id, ProjectId, Value, ParentId, Level, Path
    from IndentedProjects
    order by Path;