Relationship

Definition

A relationship in VKL describes how classes relate to each other.

Example:

Till_Haug works at Veezoo_AG
JP_Monteiro is from the segment Consumer
Rio_de_Janeiro is located in Brazil

In other words, we have the following relationships:

works_at is a relationship that goes from Employee to Company
from_segment is a relationship that goes from Customer to the class Segment
located_in is a relationship that goes from City to the class Country

Usage

import db.postgres.movie_db.public.CUSTOMER

kb {

    class Customer {
        ...

        relationship lives_in {
            
            /** How to display this relationship to the user in an answer's filters,
             * e.g. "Customer lives in Brazil" 
             * Default: "with" */
            display_name.en: "lives in"
            
            /** Specifies the cardinality of the relationship 
             *    (one of: KB_One2One, KB_Many2One, KB_Many2Many, KB_One2Many).
             * Default: KB_Many2One */
            tag: KB_Many2One

            /** lives_in is a relationship that goes from Customer to Country. */
            to: kb.Country

            /** An optional join path in the case of intermediate tables.
             *  Default: not set */
            join: [ ... ]

            /** The sql expression representing this relationship. */
            sql: "${CUSTOMER.country_id}"
        }
    }
}

Property	Optional/Mandatory	Summary	Default
to	Mandatory	A relationship is always between the outer class where it is defined and another class, specified in the property `to`.	No default
sql	Mandatory	The sql expression representing this relationship, usually a foreign key. May be omitted when it is identical to the `sql` of the `to` class (e.g. both sides use the same column of the same table), in which case Veezoo reuses that expression.	`sql` of the `to` class
display_name	Optional	How to display this relationship to the user in an answer's filters, e.g. "Customer lives in Brazil".	"with" in the respective language
tag: KB_Many2One/etc	Optional	Specifies the cardinality of the relationship (one of: KB_One2One, KB_Many2One, KB_Many2Many, KB_One2Many).	KB_Many2One
join	Optional	An optional join path in the case of intermediate tables.	Not set
to_name	Optional	A name for the class defined in `to`, e.g. to distinguish Origin Airport and Departing Airport in answers.	No default
to_synonym	Optional	A synonym for the class defined in `to`, e.g. Origin Airport can have a synonym 'Departing Airport'.	No default