Thalis Kalfigkopoulos wrote:
SELECT current_meter_reading - lag(current_meter_reading) OVER(ORDER
BY current_reading_date) AS kWh_diff, extract('days' FROM
current_reading_date - lag(current_reading_date) OVER(ORDER BY
current_reading_date)) as num_service_days FROM mytable;
How would you get the previous reading (and perhaps the previous
read date) to also appear on the same output row? The sample
table with the subtraction I showed for illustration is literally
what is printed on the bill ... they are not just presenting the
quantity used and the number of days, but actually the dates and
meter readings used to do the arithmetic.
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