Convert jsonb in PostgreSQL to rows without cycle - postgresql

Question

ffI have a json array stored in my postgres database. The first table "Orders" looks like this:
order_id, basket_items_id
1, {1,2}
2, {3}
3, {1,2,3,1}
Second table "Items" looks like this:
item_id, price
1,5
2,3
3,20
Already tried to load data with multiple sql and select of different jsonb record, but this is not a silver bullet.
SELECT
sum(price)
FROM orders
INNER JOIN items on
orders.basket_items_id = items.item_id
WHERE order_id = 3;
Want to get this as output:
order_id, basket_items_id, price
1, 1, 5
1, 2, 3
2, 3, 20
3, 1, 5
3, 2, 3
3, 3, 20
3, 1, 5
or this:
order_id, sum(price)
1, 8
2, 20
3, 33

Answer 1

demo:db<>fiddle
SELECT
o.order_id,
elems.value::int as basket_items_id,
i.price
FROM
orders o, jsonb_array_elements_text(basket_items_id) as elems
LEFT JOIN items i
ON i.item_id = elems.value::int
ORDER BY 1,2,3
jsonb_array_elements_text expands the jsonb array into one row each element. With this you are able to join against your second table directly
Since the expanded array gives you text elements you have to cast them into integers using ::int
Of course you can GROUP and SUM aggregate this as well:
SELECT
o.order_id,
SUM(i.price)
FROM
orders o, jsonb_array_elements_text(basket_items_id) as elems
LEFT JOIN items i
ON i.item_id = elems.value::int
GROUP BY o.order_id
ORDER BY 1

Answer 2

Is your orders.basket_items_id column of type jsonb or int[]?
If the type is jsonb you can use json_array_elements_text to expand the column:
SELECT
o.order_id,
o.basket_item_id,
items.price
FROM
(
SELECT
order_id,
jsonb_array_elements_text(basket_items_id)::int basket_item_id
FROM
orders
) o
JOIN
items ON o.basket_item_id = items.item_id
ORDER BY
1, 2, 3;
See this DB-Fiddle.
If the type is int[] (array of integers), you can run a similar query with the unnest function:
SELECT
o.order_id,
o.basket_item_id,
items.price
FROM
(
SELECT
order_id,
unnest(basket_items_id) basket_item_id
FROM
orders
) o
JOIN
items ON o.basket_item_id = items.item_id
ORDER BY
1, 2, 3;
See this DB-fiddle