SQL - Clone a record and its descendants

Question

I would like to be able to clone a record and its descendants in the same table. An example of my table would be the following:

Table1

id | parentid | name
---------------------
 1 |    0     |  'Food'
 2 |    1     |  'Taste'
 3 |    1     |  'Price'
 4 |    2     |  'Taste Requirements'

The "id" column is the primary key and auto-increments. The 'Food' record (i.e. where id = 1) has two records underneath it called 'Taste' and 'Price'. The 'Taste' record has a record underneath it called 'Taste Requirements'. I would like to be able to clone the 'Food' record so that Table1 would look like the following:

Table1

id | parentid | name
---------------------
 1 |    0     |  'Food'
 2 |    1     |  'Taste'
 3 |    1     |  'Price'
 4 |    2     |  'Taste Requirements'
 5 |    0     |  'Cookies'
 6 |    5     |  'Taste'
 7 |    5     |  'Price'
 8 |    6     |  'Taste Requirements'

(where 'Cookies' is the name of the new category that I want to create). I am able to select all the descendants of 'Food' using:

with Table1_CTE( id, parentid, name )
as
(
  select t.id, t.parentid, t.name from Table1 t
    where t.id = 1
  union all
  select t.id, t.parentid,t. name from Table1 t
    inner join Table1_CTE as tc
      on t.parentid = tc.id
)
select id, parentid, name from Table1_CTE

and I am able to clone just the 'Food' record (i.e. where id = 1) using:

insert into Table1 ( parentid, name )
  select ( parentid, 'Cookies' ) 
  from Table1 where id = 1

but I am having problems trying to combine the two queries to clone the descendants of 'Food'. Also, I am trying to avoid using stored procedures, triggers, curosrs, etc. Is what I am trying to do possible? I have seen some examples on the web but have been unable to apply them to my requirements.

Answer 1

As Martin suggested, you need to enable IDENTITY_INSERT so that you can push your own identity values. You may also need to acquire a table lock to ensure that Max( Id ) returns the correct value.

If object_id('tempdb..#TestData') is not null
    Drop Table #TestData
GO
Create Table #TestData
    (
    Id int not null identity(1,1) Primary Key
    , ParentId int not null
    , Name varchar(50) not null
    )
GO
Set Identity_Insert #TestData On
GO  
Insert #TestData( Id, ParentId, Name )
Values( 1,0,'Food' )
    , ( 2,1,'Taste' )
    , ( 3,1,'Price' )
    , ( 4,2,'Taste Requirement' );


With Data As
    (
    Select Cast(MaxId.Id + 1 As int) As Id
        , T.ParentId
        , 'Copy Of ' + T.name As Name
        , T.Id As OldId
        , 0 As OldParentId
    From #TestData As T
        Cross Join( Select Max( id ) As Id From #TestData ) As MaxId
    Where T.Name = 'Food'
    Union All
    Select Cast(Parent.id + Row_Number() Over( Order By Child.Id ) + 1 As int)
        , Parent.Id
        , 'Copy of ' + Child.Name
        , Child.Id
        , Child.ParentId
    From Data As Parent
        Join #TestData As Child
            On Child.ParentId = Parent.OldId
    )
Insert #TestData( Id, ParentId, Name )
Select Id, ParentId, Name
From Data
GO
Set Identity_Insert #TestData Off
GO  

Results

id | parentid | name
-- | -------- | -----------------
1  | 0        | Food
2  | 1        | Taste
3  | 1        | Price
4  | 2        | Taste Requirement
5  | 0        | Copy Of Food
7  | 5        | Copy of Taste
8  | 5        | Copy of Price
9  | 7        | Copy of Taste Requirement