group by and
sum(). Assuming that the foreign key column in
select t1.name, sum(t2.cost) total_cost from table1 t1 inner join table2 t2 on t2.t1_id = t1.id group by t1.id, t1.name
If you want to allow names that have no match in
table2, then use
left join instead, and maybe
coalesce(sum(t2.cost), 0) as well.
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