Practice SQL Window Functions | Xorthax's Trading Post

Tables Used

transaction

Column	Type
transactionid	bigint
orderid	double precision
customerid	double precision
supplierid	double precision
transactiontype	text
amount	double precision
currencyid	bigint
transactiondate	text
paymentmethod	text
description	text
status	text
createdat	text
updatedat	text

orders

Column	Type
orderid	bigint
customerid	bigint
orderdate	timestamp without time zone
totalamount	double precision
status	text

Expected Output

Column
customerid
transactiondate
amount
previouspayment

60. Payment Patterns Revealed

Track each customer's past and present payments using lag().

Xorthax is curious about payment patterns among his customers. For each payment made, show the current amount and the amount of the previous payment by the same customer.

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