Window aggregates
At a high level, a window aggregate is expressed as:
<aggr-type> (<arglist>) over (<window-spec>)aggr-typecan be the functions count, sum, avg, min, max, stddev, stddev_pop, stddev_samp, variance, var_pop, var_samp, row_number, rank, dense_rank, lead, lag, first_value, and last_value.arglistspecifies zero or more arguments to the aggregation. Only lead and lag can take more than one argument.window-specspecifies the partition columns, order columns, and framing.