Wallet Balance With Compliance Resets

SQL practice question · Hard · Window Functions · Paytm

A wallet ledger has CREDIT (adds amount), DEBIT (subtracts amount) and RESET entries. A RESET (a compliance sweep) sets the balance to exactly 0; the amount stored on a RESET row must be ignored. Entries are processed in entry_time order, ties broken by entry_id. Balances may go negative. Return entry_id, user_id, entry_type and balance_after (wallet balance right after that entry, ROUND to 2) for every entry. Order by user_id, entry_time, entry_id.

Table: wallet_ledger

Schema of wallet_ledger
ColumnType
entry_idINTEGER
user_idINTEGER
entry_timeTIMESTAMP
entry_typeTEXT
amountREAL
Sample rows of wallet_ledger
entry_iduser_identry_timeentry_typeamount
172026-01-02 09:00:00CREDIT500
272026-01-03 12:00:00DEBIT120
372026-01-10 08:00:00CREDIT200
472026-01-15 00:00:00RESETNULL
572026-01-16 10:00:00CREDIT50
692026-01-05 10:00:00CREDIT1000
792026-01-06 10:00:00DEBIT250.5
892026-01-07 10:00:00DEBIT100
Expected output on the sample data
entry_iduser_identry_typebalance_after
17CREDIT500
27DEBIT380
37CREDIT580
47RESET0
57CREDIT50
69CREDIT1000
79DEBIT749.5
89DEBIT649.5

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