Join related data in Coordinator DB ​

Use a regular SQL join when related rows are available in Coordinator DB tables or another documented local source. Distributed join modifiers and remote query execution are unavailable.

SELECT customers.id, customers.name, orders.amount
FROM customers
LEFT JOIN orders ON orders.customer_id = customers.id
ORDER BY customers.id, orders.amount;

The example assumes the two application tables already exist. A LEFT JOIN preserves customers without orders and fills the missing side with SQL NULL. If an order key has multiple matches, every matching pair contributes a row; check key uniqueness before interpreting totals.

For data held elsewhere, use a documented import workflow to create a suitable local table, validate its keys and then join it. Decide how fresh that imported copy must be and how the application will replace it. A join does not automatically synchronize an external source.

Keep right-side match conditions in ON when unmatched left rows must survive. A later WHERE predicate on the nullable right side can remove those rows. Inspect the actual plan and result cardinality before changing indexes or denormalizing the data.

See JOIN behavior, bulk input and query plans.