Is the last record in the master table related to the child?

Question

PostgreSQL

Hello. Do not prompt how correctly to implement. You need to select the last record in the parent1 table and then all the records from the child1 table related by key.
Or is there a better solution? Thanks.

SELECT  "product_id", "amount" FROM"child1" WHERE "child1"."parent_id" = (SELECT  "product_id", "amount" FROM "parent1"ORDER BY "parent1"."id" DESC LIMIT 1)

Answer 1

SELECT *
FROM (
  SELECT  "product_id", "amount"
  FROM "parent1"
  ORDER BY "parent1"."id" DESC 
  LIMIT 1
) t
UNION
SELECT  "product_id", "amount" 
FROM "child1" 
WHERE "child1"."parent_id" = (SELECT "product_id" FROM "parent1"ORDER BY "parent1"."id" DESC LIMIT 1)