Last function is used to find the last row of the selected port, optionally a filter condition can be applied.

Last is a aggregate function and can nest only one other aggregate function.
Syntax

LAST( value [, filter_condition ] )

Argument	Required/Optional	Description
value	Required	Any datatype except Binary. Passes the values for which you want to return the last row. You can enter any valid transformation expression.
filter_condition	Optional	Limits the rows in the search. The filter condition must be a numeric value or evaluate to TRUE, FALSE, or NULL. You can enter any valid transformation
expression.

When last row has null value, it returns previous value. If all the values are null, last function returns NULL output.
Example : Find the last employee who's salary is above 5000

LAST(Employee,salary >5000)

Employee	Salary
Shawn	4500
Mark	6000
Bill	2000
Flora	5500
Eliza	6000

Output : Eliza