Relationships

A join is used to combine rows from two or more tables, based on a related column between them.

Declaration

In Forest, relations are defined as fields and are traversable in only one direction.

Four join types are available: ManyToOne, ManyToMany, OneToMany, and OneToOne.

Type	Where are the common keys?
ManyToOne	`origin[foreignKey] == foreign[foreignKeyTarget]`
OneToMany	`origin[originKeyTarget] == foreign[originKey]`
ManyToMany	`origin[originKeyTarget] == through[originKey] && though[foreignKey] == foreign[foreignKeyTarget]`
OneToOne	`origin[originKeyTarget] == foreign[originKey]`