php - How to merge and sum up certain values of items that have the same ID value

one text

Solution:

SELECT name, 
       SUM(quantity * pack_value) AS quantity,
       1 AS pack_value,
       order_id
FROM order_items
GROUP BY name,
         order_id;

fiddle

Merge another tables to this code using it as subquery, or add them into FROM clause (adjusting its output list and grouping expression) if needed.

Source