Account balances and activity

The bank dataset belongs to Rawabi Bank, a fictional Saudi retail bank. accounts holds each account with its opening_balance on 2024-01-01; transactions holds every posting from then to the end of 2025.

Two conventions matter more than anything else here:

• amount is always positive. direction says which way money moved from the customer's point of view: credit = into the account, debit = out of it. The signed amount is CASE WHEN direction = 'credit' THEN amount ELSE -amount END.
• Balance at time t = opening_balance + signed transactions with posted_at <= t. Nothing is stored: the balance is derived.

Credit cards and personal finance accounts carry negative balances: they show what the customer owes. A card purchase is a debit (the balance goes further negative), a repayment a credit.

Notice that this is the bank's customer view. In the general ledger of the previous lessons, a debit to cash increased it; here a debit to a customer's account decreases it, because for the bank a customer deposit is a liability. Always check which perspective a dataset uses before you sign anything.