SELECT SUBSTRING(user__field_fio.field_fio_value, 1, 1) AS field_fio_value_truncated,
       COUNT(users_field_data.uid) AS num_records,
       'polzovateli_s_citatami:attachment_1' AS view_name,
       MIN(users_field_data.uid) AS UID,
       MIN(node_field_data_users_field_data.nid) AS node_field_data_users_field_data_nid
FROM {users_field_data} users_field_data
LEFT JOIN {node_field_data} node_field_data_users_field_data ON
  (SELECT node_field_dataINNER.nid AS nidINNER,
          ':default' AS view_name
   FROM {node_field_data} node_field_dataINNER
   LEFT JOIN {users_field_data} users_field_data_node_field_dataINNER ON "node_field_dataINNER".uid = "users_field_data_node_field_dataINNER".uid
   WHERE ((("users_field_data_node_field_dataINNER".uid = users_field_data.uid)))
   ORDER BY node_field_dataINNER.nid DESC LIMIT 1
   OFFSET 0) = node_field_data_users_field_data.nid
LEFT JOIN {user__field_fio} user__field_fio ON users_field_data.uid = user__field_fio.entity_id
AND (user__field_fio.deleted = :views_join_condition_0
     AND user__field_fio.langcode = users_field_data.langcode)
WHERE (((users_field_data.status = :db_condition_placeholder_2)
        AND (node_field_data_users_field_data.type IN (:db_condition_placeholder_3))))
GROUP BY field_fio_value_truncated,
         view_name
ORDER BY field_fio_value_truncated ASC LIMIT 10
OFFSET 0;

Array ([:db_condition_placeholder_2] => 1 [:db_condition_placeholder_3] => citaty [:views_join_condition_0] => 0)