Rlookup
relational-functions rlookup
syntax
- rlookup(foreign_key, primary_key)
definition
rlookup(foreign_key, primary_key) results in a relation from the domain-unit of the foreign_key argument towards the domain unit of the primary key argument
applies to
- foreign_key: an attribute which can serve as primary key for the domain unit of the primary_key argument, e.g. a region code.
- primary_key: an attribute which can serve as primary key for it’s own domain unit and with the the same values-unit as the foreign_key attribute.
description
We advise that the second argument can be used as primary key for the domain unit of this argument.
If multiple instances of the second argument occur, the resulting value will be the first index number found.
applies to
- attributes foreign_key and primary_key with Numeric, Point, uint2, unit4, bool or string value-type
conditions
The values unit of the arguments foreign_key and primary_key must match.
example
attribute<Region> Region_rel (City) := rlookup(City/RegionCode, Region/RegionCode);
| City/RegionCode | Region_rel |
|---|---|
| 100 | 0 |
| 200 | 1 |
| 300 | 2 |
| 200 | 1 |
| 400 | 3 |
| null | null |
| 400 | 3 |
domain City, nr of rows = 7
| Region/RegionCode |
|---|
| 100 |
| 200 |
| 300 |
| 400 |
| 500 |
domain Region, nr of rows = 5