Detta är en förenklad version av @a_horse's korrekta svara
(efter diskussion med OP i kommentarer).
Fungerar med alla (rimligt ändligt) antal nivåer i rekursionen.
Totalt pris för given project_id
WITH RECURSIVE cte AS (
SELECT project_id AS project_parent, project_value
FROM projects
WHERE project_id = 1 -- enter id of the base project here !
UNION ALL
SELECT p.project_id, p.project_value
FROM cte
JOIN projects p USING (project_parent)
)
SELECT sum(project_value) AS total_value
FROM cte;
Totalpris för alla projekt
WITH RECURSIVE cte AS (
SELECT project_id, project_id AS project_parent, project_value
FROM projects
WHERE project_parent IS NULL -- all base projects
UNION ALL
SELECT c.project_id, p.project_id, p.project_value
FROM cte c
JOIN projects p USING (project_parent)
)
SELECT project_id, sum(project_value) AS total_value
FROM cte
GROUP BY 1
ORDER BY 1;
db<>fiol här
(med korrekt testfall)
Gammal sqlfiddle