Rlookup
Relational functions rlookup
- rlookup(foreign_key, primary_key)
rlookup(foreign_key, primary_key) results in a relation from the domain of the foreign_key argument towards the domain of the primary key argument .
- foreign_key: an attribute which can serve as primary key for the domain 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 and with the the same values unit as the foreign_key attribute.
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.
- attributes foreign_key and primary_key with Numeric, Point, uint2, unit4, bool or string value type
The values unit of the arguments foreign_key and primary_key must match.
attribute 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
