"David G. Johnston" <david.g.johnston@gmail.com> writes:
> I was going to write basically that but something feels off to me. Maybe
> something like this:
> "As shown here, the rank function produces a numerical ranking within each
> partition, using the order defined by the ORDER BY clause. Ranking assigns
> the same rank to all rows that tie according to the order by criteria,
> while still incrementing the rank counter. Thus there are gaps in the
> serial numbering. These can be removed by instead using the dense_rank
> window function. Ties can instead be given their own unique value by using
> the row_number window function. In all these cases, as the window function
> is effectively just counting rows, the function itself has no input
> parameter."
> If we don't want to get into that level of nuance in the tutorial I suggest
> we use the row_number() window function instead of rank, and just say
> because we count rows no parameter is needed.
Yeah, I was wondering if it'd be worth bringing up dense_rank,
but decided "probably not". I like your idea of switching the
example to use row_number to simplify things. What would the
text be then? Perhaps
As shown here, the <function>row_number</function> function
assigns sequential numbers to the rows within each partition,
in the order defined by the <literal>ORDER BY</literal> clause
(with tied rows numbered in an unspecified order).
<function>row_number</function> needs no explicit parameter,
because its behavior
is entirely determined by the <literal>OVER</literal> clause.
regards, tom lane
