Copy data from same table based on other columns - sql-server

Question

I have a table named tableX structed like this. Notice the relation of childNo and parentNo columns.
childNo | parentNo |locationId |value
--------+----------+-----------+--------+
26 | NULL | 7 | value1 |
27 | NULL | 7 | value2 |
28 | 27 | 7 | value3 |
29 | 27 | 7 | value4 |
30 | 27 | 7 | value5 |
34 | NULL | 7 | value6 |
and I want to copy the same value column information to a different locationId(let's say locationId = 3) with new childNo and parentNo (protecting the relation)
Expected output.
childNo | parentNo |locationId |value
--------+----------+-----------+--------+
36 | NULL | 3 | value1 |
37 | NULL | 3 | value2 |
38 | 37 | 3 | value3 |
39 | 37 | 3 | value4 |
40 | 37 | 3 | value5 |
44 | NULL | 3 | value6 |
How can I achieve that using T-SQL?

Answer 1

Perhaps I'm missing something, but you could just do:
insert into t(childNo, parentNo, locationId, value)
select t.childNo + 10, t.ParentNo + 10, 3, t.value
from t
where t.locationId = 7;

Answer 2

I try this sample in SQL Server 2012.
DECLARE #lastParent int;
DECLARE #lastChild int;
DECLARE #newLocationId int;
SET #newLocationId = 3;
SELECT #lastParent = MAX(ParentNo) FROM tableX WHERE ParentNo IS NOT NULL;
SELECT #lastChild = MAX(ChildNo) from tableX;
INSERT INTO tableX (childNo, parentNo , LocationId, valueColumn)
SELECT
#lastChild + ROW_NUMBER() OVER (PARTITION BY LocationId ORDER BY childNo) AS childNo,
CASE WHEN (ParentNo IS NOT NULL) then #lastParent + 1
ELSE ParentNo
END as NewParentNo,
#NewLocationId as NewLocationId, valueColumn
FROM tableX
WHERE LocationId = 7
ORDER BY childNo
Two instances of this code running at same time, can produce duplicates values. I think your table must have Unique constraint on childNo and some trigger to validate parentNo