Invert
relational-functions invert
syntax
- invert(relation)
definition
invert(a) inverts the relation argument.
Inverting means the resulting attribute has as domain-unit the values-unit and as values unit the domain unit of the relation argument.
applies to
- attribute relation with value-type of the group CanBeDomainUnit
example
attribute<Region> invertRegion_rel (Region) := invert(City/Region_rel);
| City/Region_rel |
|---|
| 0 |
| 1 |
| 2 |
| 1 |
| 3 |
| null |
| 3 |
domain City, nr of rows = 7
| InvertRegion_rel |
|---|
| 1 |
| 4 |
| 3 |
| 7 |
| null |
domain Region, nr of rows = 5