UPDATE {tenantId}_mod_source_record_storage.records_lb as rec
SET external_id = (record_instance_ids.instance_id)::uuid
FROM (
    SELECT id, ids_subfields ->> 'i' AS instance_id
    FROM (
        SELECT id, fields
        FROM {tenantId}_mod_source_record_storage.marc_records_lb, jsonb_array_elements(content -> 'fields') as fields
        WHERE fields ? '999'
    ) as ids_fields, jsonb_array_elements(fields -> '999' -> 'subfields') AS ids_subfields
    WHERE ids_subfields ? 'i'
) AS record_instance_ids
WHERE rec.id = record_instance_ids.id AND external_id IS NULL;