UNPACK


Extracts the value from a single valued collection or list. Is the inverse of the LIST function.


Syntax

UNPACK ( collection/list )


Input
  • collection/list - A collection or list of one entity or attribute instance.


Return type

  • entity instance
  • attribute value of any type


Examples

Suppose the following data model.


Person.namePerson.SequenceNumber
“Bob”654
“Jane”523
“Mary”667
“Rick”500
“Ron”490
“Jenny”765

  • UNPACK ( COLLECT Person.name FROM ALL Person WHERE ( Person.SequenceNumber = MIN ( COLLECT Person.SequenceNumber FROM ALL Person ) ) ) = “Ron”

  • In case a second entry "Ron","490" exists, the expression UNPACK ( COLLECT Person.name FROM ALL Person WHERE ( Person.SequenceNumber = MIN ( COLLECT Person.SequenceNumber FROM ALL Person ) ) ) will fail, because the UNPACK cannot resolve a list with two elements. To solve this the UNIQUE function has to be used: UNPACK ( UNIQUE ( COLLECT Person.name FROM ALL Person WHERE ( Person.SequenceNumber = MIN ( COLLECT Person.SequenceNumber FROM ALL Person ) ) ) ) = "Ron".

  • UNPACK ( COLLECT Person.name FROM ALL Person WHERE ( Person.SequenceNumber = MAX ( COLLECT Person.SequenceNumber FROM ALL Person ) ) ) = “Jenny”