first

Description

Return the first 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

storable value

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

• Aggregate

• Window

Usage

first(expression, [ order_by ])

Argument	Type	Optional	Repeatable	Restrictions
expression	storable value	no	no	none
order_by	ordering	yes	no	constant

Examples

make_col first_customer:window(first(customer_id), group_by(category))

Find out the customer that appears first within each category.

statsby first_customer:first(customer_id), group_by(category)

Find out the customer that appears first within each category.

statsby first_customer:first(customer_id, order_by(login_time)), group_by(category)

Find out the customer that logged in first within each category.