First value: first_value

Syntax

in a Data Set expression	first_value ( dataset over ( analyticClause ) )
in a Component expression within a calc clause	first_value ( component over ( analyticClause ) )

Input parameters

dataset	the operand Data Set
component	the operand Component
analyticClause	see Analytic invocation

Semantics for scalar operations

This operator cannot be applied to scalar values.

Input parameters type

dataset

dataset { measure<scalar> _+ }

component

component<scalar>

Result type

result

dataset
| component<scalar>

Additional Constraints

The Aggregate invocation is not allowed.

Behaviour

The operator returns the first value (in the value order) of the set of Data Points that belong to the same analytic window as the current Data Point.

When invoked at Data Set level, it returns the first value for each Measure of the input Data Set. The first value of different Measures can result from different Data Points. When invoked at Component level, it returns the first value of the specified Component.

For other details, see Analytic invocation.

Examples

Given the operand dataset DS_1:

Input DS_1 (see structure)

Id_1	Id_2	Id_3	Me_1	Me_2
A	XX	1993	3	1
A	XX	1994	4	9
A	XX	1995	7	5
A	XX	1996	6	8
A	YY	1993	9	3
A	YY	1994	5	4
A	YY	1995	10	2
A	YY	1996	2	7

Example 1

DS_r := first_value ( DS_1 over ( partition by Id_1, Id_2 order by Id_3 data points between 1 preceding and 1 following));

results in (see structure):

DS_r

Id_1	Id_2	Id_3	Me_1	Me_2
A	XX	1993	3	1
A	XX	1994	3	1
A	XX	1995	4	9
A	XX	1996	7	5
A	YY	1993	9	3
A	YY	1994	9	3
A	YY	1995	5	4
A	YY	1996	10	2