Linking entities

The link entity syntax

linkEntity:
    entityName [FROM propertyName] TO propertyName [LINK TYPE <LEFT | RIGHT | INNER>]

Examples

Simple one-to-many relationship

For the purpose of this example we will use two related entities, with the following schema:

Example 1 
FETCH product (name AS productName) {
    unit_of_measure TO id_unit_of_measure (name AS unitOfMeasureName)
}

The example will fetch the product name and the name for the related unit of measure. Notice here that the FROM directive is missing, because the link property id_unit_of_measure has the same name in both entities.

Multiple one-to-many relationships

For the purpose of this example we will use two related entities, with the following schema:

Example 2 
FETCH product (name AS productName) {
    unit_of_measure TO id_unit_of_measure (name AS unitOfMeasureName),
    unit_of_measure FROM id_unit_of_measure TO id_unit_of_measure_sale (name AS saleUnitOfMeasureName)
}

The example will fetch the product name, the name for the related unit of measure and the name for the related unit of measure for sale. This example has a double one-to-many relationship between product and unit_of_measure, so both FROM and TO directives need to be used.

If you have a one-to-many relationship the FROM directive indicates the column of the one (unit_of_measure in this example) entity and the TO directive indicates the column of the many (product in this example) entity.

← Aggregation
The basics →