The Flag List

Any withdrawal of 500 dollars or more at Northline Bank goes to a human for review. Building that flag list is less obvious than it sounds, because the ledger records outflows as negative numbers — so the movements the reviewer cares about are the ones furthest below zero, not the ones above a threshold.

transactions — one row per movement of money. customer_id points at a row in customers; type is one of deposit, withdrawal or transfer; txn_date is the day it settled. The ledger is signed: money arriving in an account is stored as a positive amount, and money leaving it as a negative one, so a 600-dollar withdrawal is recorded as -600.

The table already exists in the database — there is nothing to create or load.

Task: Write a query that returns three columns — id, customer_id and amount — for every withdrawal of 500 dollars or more. Show the largest withdrawal first, which in this signed ledger means the most negative amount first; two withdrawals of the same amount come back with the smaller id first. Transfers are not withdrawals and must not appear.

Example output — shape only, on invented movements. The largest withdrawal is the most negative amount, so it heads the list: