PostgreSQL: advanced patterns with JSONB column and array aggregation in subquery
I'm relatively new to this, so bear with me. I've looked through the documentation and I'm still confused about I'm working with an scenario when trying to aggregate JSONB data in a PostgreSQL 13 database. I have a table called `orders` where each order can have multiple items stored in a JSONB column named `order_items`. I'm trying to retrieve a list of unique item IDs from these JSONB objects for each order. The query I wrote is as follows: ```sql SELECT order_id, (SELECT jsonb_agg(DISTINCT item_id) FROM jsonb_array_elements(order_items -> 'items') AS item WHERE item ->> 'item_id' IS NOT NULL) AS unique_item_ids FROM orders; ``` However, I'm getting an unexpected result. Instead of a list of unique item IDs, I'm seeing duplicates in the aggregated JSONB array. After some debugging, I noticed that when the JSONB contains multiple entries with the same `item_id`, they get included multiple times in the result. I tried modifying the inner query to explicitly cast `item ->> 'item_id'` to a text to ensure I'm aggregating the same type, but it didn't resolve the duplication: ```sql SELECT order_id, (SELECT jsonb_agg(DISTINCT (item ->> 'item_id')::text) FROM jsonb_array_elements(order_items -> 'items') AS item) AS unique_item_ids FROM orders; ``` Still, this produces the same results. Is there a more effective way to ensure that I get a truly unique list of item IDs from this JSONB array? Any insights or alternative approaches would be greatly appreciated! For context: I'm using Sql on Windows. I'd really appreciate any guidance on this. Any ideas what could be causing this?