Compute Delta Between Events

The monday Work Management team wants to monitor how long items remain open on a board. Given separate creation and completion event tables, write a PostgreSQL query that calculates the elapsed time between the two timestamped events for every created item.

Requirements

1. Start with every item in item_created_events, including items without a completion event.
2. Join a matching completion event from item_completed_events using item_id.
3. Return the elapsed time in hours as delta_hours, rounded to two decimal places. Return NULL when the completion timestamp is unavailable.
4. Order the results chronologically by the creation timestamp.