last_value
Selects the last encountered value, similar to anyLast, but could accept NULL.
Mostly it should be used with Window Functions.
Without Window Functions the result will be random if the source stream is not ordered.
examples
Example 1
The NULL value is ignored at default.
Example 2
The NULL value is ignored.
Example 3
The NULL value is accepted.
Example 4
Stabilized result using the sub-query with ORDER BY.