Common Table Expression in sqlite using rowid - sqlite

Question

I found a good article on converting adjacency to nested sets at http://dataeducation.com/the-hidden-costs-of-insert-exec/
The SQL language used is Microsoft SQL Server (I think) and I am trying to convert the examples given in the article to sqlite (as this is what I have easy access to on my Macbook).
The problem I appear to be having is converting the part of the overall CTE query to do with the Employee Rows
EmployeeRows AS
(
SELECT
EmployeeLevels.*,
ROW_NUMBER() OVER (ORDER BY thePath) AS Row
FROM EmployeeLevels
)
I converted this to
EmployeeRows AS
(
SELECT
EmployeeLevels.*,
rowid AS Row
FROM EmployeeLevels
ORDER BY thePath
)
and the CTE query runs (no syntax errors) but the output I get is a table without the Row and Lft and Rgt columns populated
ProductName ProductID ParentProductID TreePath HLevel Row Lft Rgt
----------- ---------- --------------- ---------- ---------- ---------- ---------- ----------
Baby Goods 0 0 1
Baby Food 10 0 0.10 2
All Ages Ba 100 10 0.10.100 3
Strawberry 200 100 0.10.100.2 4
Baby Cereal 250 100 0.10.100.2 4
Beginners 150 10 0.10.150 3
Formula Mil 300 150 0.10.150.3 4
Heinz Formu 310 300 0.10.150.3 5
Nappies 20 0 0.20 2
Small Pack 400 20 0.20.400 3
Bulk Pack N 450 20 0.20.450 3
I think the start of the problem is the Row is not getting populated and therefore the Lft and Rgt columns do not get populated by the following parts of the query.
Are there any sqlite experts out there to tell me:
am I translating the rowid part of the query correctly
does sqlite support a rowid in a part of a CTE query
is there a better way? :)
Any help appreciated :)

Answer 1

am I translating the rowid part of the query correctly
No.
The SQL:
SELECT
EmployeeLevels.*,
rowid AS Row
FROM EmployeeLevels
ORDER BY thePath
has the Row defined as the rowid of table EmployeeLevels in SQLite, ignoring the order clause. Which is different from the intention of ROW_NUMBER() OVER (ORDER BY thePath) AS Row
does sqlite support a rowid in a part of a CTE query
Unfortunately no. I assume you mean this:
WITH foo AS (
SELECT * FROM bar ORDER BY col_a
)
SELECT rowid, *
FROM foo
but SQLite will report no such column of rowid in foo.
is there a better way?
Not sure it is better but at least it works. In SQLite, you have a mechanism of temp table which exists as long as your connection opens and you didn't delete it deliberately. Rewrite the above SQL in my example:
CREATE TEMP TABLE foo AS
SELECT * FROM bar ORDER BY col_a
;
SELECT rowid, *
FROM foo
;
DROP TABLE foo
;
This one will run without SQLite complaining.
update:
As of SQLite version 3.25.0, window function is supported. Hence you can use row_number() over (order by x) expression in your CTE if you happen to use a newer SQLite