sql - Need helt with MySQL query

Question

I would like some help with a query on a personal project that I can′t figure out by myself. Im trying to summerize usedQuantity by the productId from three diffrent tables in one query.

SQL result I would like:

productId	TOTAL usedQuantity
10	20
20	20
50	100
60	120

question from:https://stackoverflow.com/questions/66059258/need-helt-with-mysql-query

Answer 1

seems you need the sum of the table's union

select productId, sum(usedQuantity) usedQuantity
from (
   select productId, usedQuantity
   from  table_one
   union all
   select productId, usedQuantity
   from  table_two
   union all
   select productId, usedQuantity
   from  table_three ) t
group by productId