RDBMS Type: MySQL
Returns the percentage of partition values less than the value in the
current row, excluding the highest value. Return values range from 0 to
1 and represent the row relative rank, calculated as the result of this
formula, where rank is the row rank and rows is the number of partition
(rank - 1) / (rows - 1)
This function should be used with ORDER BY to sort partition rows into
the desired order. Without ORDER BY, all rows are peers.
over_clause is as described in
For an example, see the CUME_DIST() function description.