select

selection-functions select

syntax

  • select(condition)
  • select_uint8(condition)
  • select_uint16(condition)
  • select_uint32(condition)
  • select_uint64(condition)

definition

Like the subset function, the select(condition) function results in a new uint32 domain-unit for which the values of the condition argument are true.

The difference with the subset/select_with_org_rel function is that the select does not result in a generated subitem (nr_OrgEntity for subset, org_rel for select_with_org_rel).

This makes the select function useful to apply on large domain units for which the nr_OrgEntity or org_rel could use a substantial amount of memory.

Between versions 7.305 and 8.7.2 the name select_unit was used for the select function.

The explicit select_uint8, select_uint16, select_uint32 and select_uint64 functions can be used in the same manner as the select function, to create a new domain unit with the explicit value type.

description

Use the select_data function to relate attributes to the new domain unit, see the example.

applies to

  • condition must be a boolean attribute or subexpression resulting in boolean values.

since version

8.8.0

example

unit<uint32> ZHCities := select(City/RegionCode == 200)
{
   attribute<string> name := select_data(., City/RegionCode == 200, City/Name);
}
City/RegionCode City/Name
100 Amsterdam
200 Rotterdam
300 Utrecht
200 Den Haag
400 Eindhoven
null Haarlem
400 Tilburg

domain City, nr of rows = 7

ZHCities/name
Rotterdam
Den Haag

domain ZHCities, nr of rows = 2

see also