Oracle sucks

SELECT
 "alias6".birth_date AS "col4",
 "alias6".e_category AS "col5",
 "alias6".id_chief AS "col6",
 "alias6".id_department AS "col7",
 "alias6".fire_date AS "col8",
 "alias6".first_name AS "col9",
 "alias6".hire_date AS "col10",
 "alias6".id_employee AS "col11",
 "alias6".last_name AS "col12",
 "alias6".dtm_modified AS "col13",
 "alias6".salary AS "col14",
 "alias6".e_sex AS "col15",
 "alias6".id_product AS "col16"
FROM (
 SELECT "alias1".id_employee AS "col123",
  CASE WHEN (EXISTS (
    SELECT '1' AS "col1"
    FROM t_employee "alias2"
    WHERE "alias2".id_chief = "alias1".id_employee
   ))
  THEN ("alias1".id_employee) ELSE ("alias1".id_chief) END AS "col2"
 FROM t_employee "alias1"
 /* ORDER BY "alias1".id_employee - если раскомментировать, результат запроса меняется! */
) "alias4"
LEFT JOIN (t_employee "alias3"
 LEFT JOIN (t_employee "alias5"
  LEFT JOIN t_employee "alias6" ON "alias5".id_chief = "alias6".id_employee
 ) ON "alias3".id_chief = "alias5".id_employee
) ON "alias4"."col2" = "alias3".id_employee
ORDER BY "alias4"."col123"