The first_value(…, 'ignore nulls') window function with the string argument 'ignore nulls' is not standard SQL. It evaluates the expression in the rows defined by the over clause in order and returns the first non-null value (if any).
SELECT FIRST_VALUE(<expr>, 'IGNORE NULLS') OVER (ORDER BY …)
FROM …Related
Same functionality in standard SQL:
first_value(…) ignore nulls
Normative References
'Ignore nulls' as second argument to first_value() is not covered in the international SQL standard ISO/IEC 9075-2:2023. In standard SQL the ignore nulls clause follows the parentheses: first_value() ignore nulls.
