Whether a function's output can be null: all but the counts and the rank
functions, though the engine types Sum and Average as never null (PLAN
§5.7, D4), and Median, Std Dev, Variance and Join Text too, which are empty
on a group of empty values, and Std Dev and Variance on a group of one row
(PLAN §11.28); a row function's is empty when there is no such row (PLAN
§11.9). It decides rows: a negated filter guards with isEmpty only on a
nullable column.
Whether a function's output can be null: all but the counts and the rank functions, though the engine types Sum and Average as never null (PLAN §5.7, D4), and Median, Std Dev, Variance and Join Text too, which are empty on a group of empty values, and Std Dev and Variance on a group of one row (PLAN §11.28); a row function's is empty when there is no such row (PLAN §11.9). It decides rows: a negated filter guards with
isEmptyonly on a nullable column.