leveraging_window_functions

🛠 Leveraging Window Functions

Window functions let you perform calculations across sets of rows related to the current row. Use them for running totals, ranks, or moving averages directly in SQL.

Invoice.select(
  "invoices.*, SUM(amount) OVER (PARTITION BY customer_id ORDER BY created_at) AS running_total"
)

Here, running_total is computed per customer in chronological order without additional Ruby processing.