first_not_null¶
Description¶
Return the first non-null value of one column across an ordered group.
If no ordering is specified, the default ordering is that of the invoking verb, which is generally the ‘valid_from’ timestamp, ascending. In this case, the first value is the earliest.
Return type¶
expression
Domain¶
This is an aggregate function (aggregates rows over a group in aggregate verbs.)
This is a window function (calculates over a group of multiple input rows using windowing.)
Categories¶
Usage¶
first_not_null(expression, [ order_by ])
Argument |
Type |
Optional |
Repeatable |
Restrictions |
|---|---|---|---|---|
expression |
storable |
no |
no |
none |
order_by |
ordering |
yes |
no |
constant |
Examples¶
make_col first_value:window(first_not_null(value), group_by(kind))
Find out the first non-null within each kind.
statsby first_customer:first_not_null(customer_id), group_by(category)
Find out the first non-null customer within each category.
statsby first_customer:first_not_null(customer_id, order_by(login_time)), group_by(category)
Find out the non-null customer that logged in first within each category.