Unique

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Relational functions unique

Contents

syntax

  • unique(a)

definition

unique(a) results in a new uint32 domain unit with the unique occurences of attribute a.

description

The unique function generates a subitem, named Values. This data item contains the unique occurences of attribute a, sorted ascending.

The Values data item can be used in a lookup (in case attribute a is a relation) or a rjoin function, to relate attributes to the new domain unit, see the example.

applies to

  • attribute a with Numeric, Point, uint2, uint4, bool or string value type

since version

5.15

example

unit<uint32> Region := unique(City/RegionCode)
{
   attribute<string> name := rjoin(Values, City/RegionCode, City/RegionName);
}
City/RegionCode City/RegionName
100 Noord Holland
200 Zuid Holland
300 Utrecht
200 Zuid Holland
400 Noord Brabant
null null
400 null

domain City, nr of rows = 7

Region/Values Region/name
100 Noord Holland
200 Zuid Holland
300 Utrecht
400 Noord Brabant
null null

domain Region, nr of rows = 5

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