# 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.

any

## 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.)

## Usage¶

first_not_null( expression [ , order_by ] )


Argument

Type

Required

Multiple

expression

any

Required

Only one

order_by

ordering

Optional

Only one

## 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.