Union_data

relational-functions union_data

syntax

definition

union_data(domain unit, a, b, .. n) results in a new attribute with as domain-unit the first argument: domainunit.

The resulting attribute contains the values of the data-item a, b, .., n.

description

The first argument domainunit, is often made with the union_unit function.

The union_data function results in an attribute with as values-unit the values units of data items a, b, ..n and as domain-unit the first argument of the function (domainunit). In other words, it appends b to a and then c to a and b, etc.

union_data(newdomain, att_old_domain) can be used to convert attributes from a source to a target domain unit.

applies to

  • unit domainunit with value-type from the group CanBeDomainUnit
  • data items a, b, … n with Numeric, Point, uint2, uint4, bool or string value type

conditions

  • The values unit of data items a, b, … n must match.

example

unit<uint32> HollandCity := union_unit(NHCity, ZHCity)
{
   attribute<string> name := union_data(., NHCity/name, ZH/City/name);
}
HollandCity/name
Amsterdam
Haarlem
Alkmaar
Rotterdam
DenHaag
Leiden
Dordrecht
Leiden

domain HollandCity, nr of rows = 8

NHCity/name
Amsterdam
Haarlem
Alkmaar

domain NHCity, nr of rows = 3

ZHCity/name
Rotterdam
DenHaag
Leiden
Dordrecht
Leiden

domain ZHCity, nr of rows = 5

see also