The last_value(… ignore nulls) window function with the ignore nulls inside the parentheses is not standard SQL. It evaluates its argument in the rows defined by the over clause in reverse order and returns the first non-null value (if any).
SELECT LAST_VALUE(<expr> IGNORE NULLS) OVER (ORDER BY …)
FROM …Default Framing Applies
If there is no explicit framing clause the following default applies:
RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROWThat means, the last_value() function cannot see beyond the ties to the current row. Open the frame to bring the last row into reach:
ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWINGRelated
Same functionality in standard SQL:
last_value(…) ignore nulls
Normative References
Ignore nulls inside the parentheses of last_value() is not covered in the international SQL standard ISO/IEC 9075:2016-2. In standard SQL the ignore nulls clause follows the parentheses: last_value() ignore nulls.
