RELATED() vs EXTEND()

The EXTEND() operation is the general-purpose mechanism for joining features across entities. The RELATED() function family provides a more concise and easier to understand syntax for simple cases.

Use RELATED() if possible, and EXTEND() when you need work with many foreign keys or require more explicit control over the binding logic.

foreign key ↔ primary key

FeatureQL

SELECT
    CUSTOMER_ID,
    ORDER_CITY_RELATED := RELATED(TABLES.FCT_ORDERS[order_city_name] VIA TABLES.AGG_CUSTOMERS_OBT[last_order_id]),
    ORDER_CITY_EXTEND := EXTEND(
        ROW(TABLES.AGG_CUSTOMERS_OBT[last_order_id] as last_order_id)
        WITH TABLES.FCT_ORDERS[order_city_name] as CITY_NAME
        VIA last_order_id BOUND TO ORDER_ID
    )[CITY_NAME]
FROM FM.ECOMM
FOR
    CUSTOMER_ID := BIND_VALUES(SEQUENCE(100,102)),
;

Result

FM.ECOMM.CUSTOMER_ID BIGINT	ORDER_CITY_RELATED VARCHAR	ORDER_CITY_EXTEND VARCHAR
100	Barcelona	Barcelona
101	Barcelona	Barcelona
102	Barcelona	Barcelona

foreign key ↔ foreign key

FeatureQL

SELECT
    CUSTOMER_ID,
    NUM_ORDERS_RELATED := RELATED(SUM(1) GROUP BY TABLES.FCT_ORDERS[order_customer_id] VIA CUSTOMER_ID),
    NUM_ORDERS_EXTEND := EXTEND(
        ROW(CUSTOMER_ID as CUSTOMER_ID)
        WITH SUM(1) GROUP BY TABLES.FCT_ORDERS[order_customer_id] as num_orders
        VIA CUSTOMER_ID BOUND TO TABLES.FCT_ORDERS[order_customer_id]
    )[num_orders]
FROM FM.ECOMM
FOR
    CUSTOMER_ID := BIND_VALUES(SEQUENCE(100,102)),
    ORDER_ID := BIND_VALUES(SEQUENCE(200,203)),
;

Result

FM.ECOMM.CUSTOMER_ID BIGINT	NUM_ORDERS_RELATED BIGINT	NUM_ORDERS_EXTEND VARCHAR
100	2	2
101	1	1
102	1	1

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Last update at: 2026/02/16 15:46:17

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foreign key ↔ primary key foreign key ↔ foreign key