问题
Follow-up to this answered question:
Complex nested aggregations to get order totals
After getting it answered I realized that it would be much easier if I start of with:
Budget.find(2).cbs_items.order('cbs_items.name ASC').select(:id, :name)
Budget Load (0.3ms) SELECT "budgets".* FROM "budgets" WHERE "budgets"."company_id" = 9 AND "budgets"."id" = $1 LIMIT $2 [["id", 2], ["LIMIT", 1]]
CbsItem Load (1.6ms) SELECT "cbs_items"."id", "cbs_items"."name" FROM "cbs_items" INNER JOIN "cost_breakdown_structures" ON "cbs_items"."cost_breakdown_structure_id" = "cost_breakdown_structures"."id" AND "cbs_items"."company_id" = "cost_breakdown_structures"."company_id" WHERE "cost_breakdown_structures"."company_id" = 9 AND "cbs_items"."company_id" = 9 AND "cost_breakdown_structures"."id" = $1 ORDER BY cbs_items.name ASC [["id", 2]]
=> [#<CbsItem:0x00007f7f4605c3b0 id: 9, name: "100">, #<CbsItem:0x00007f7f460569b0 id: 10, name: "200">, #<CbsItem:0x00007f7f4604f908 id: 11, name: "300">]
Ignore the company_id references - part of my multi-tenant code. In my view I get the list of cbs_items all sorted. Now I want to layer on the answer from the previous question.
I revised the other Fiddle answer to get the results I am looking for:
https://dbfiddle.uk/?rdbms=postgres_11&fiddle=e521b78ff8e8d4e7d9bba0eee37d5dd5
I am not sure how to pose the actual question here.
I can work with the result from this as raw SQL but in a Rails app it's less than ideal. I am sure I can this work but I think it has to start with SELECT "cbs_items"."id"... FROM "cbs_items"... and add the subqueries onto that. Rails Active Record seems to support subqueries.
So to start perhaps: How would I modify the above Fiddle to start with?:
SELECT ... FROM "cbs_items" ...
In this answer:
Rails raw SQL example
I could use CbsItem.find_by_sql(... to convert this to a normal Rails active record call.
来源：https://stackoverflow.com/questions/61706844/complex-nested-aggregations-to-get-order-totals-part-2