[SQL] SUM() & GROUP BY

[Muhyiddin A.M Hayat]

hotel=# SELECT hotel-#   "public".billing.id, hotel-#   "public".billing.guest_id, hotel-#   "public".billing.trx_date, hotel-#   "public".billing.trx_time, hotel-#   "public".billing.payment_method, hotel-#   "public".billing.tax, hotel-#   "public".billing.dep_id, hotel-#   "public".department."name", hotel-#   SUM("public".items.price) AS total, hotel-#   "public".billing.amount_paid hotel-# FROM hotel-#   "public".billing_items hotel-#   INNER JOIN "public".billing ON ("public".billing_items.billing_id = "public".billing.id) hotel-#   INNER JOIN "public".department ON ("public".billing.dep_id = "public".department.id) hotel-#   INNER JOIN "public".items ON ("public".billing_items.items_id = "public".items.id) hotel-# GROUP BY  "public".billing.id; ERROR:  Attribute billing.guest_id must be GROUPed or used in an aggregate function hotel=#   What Worng ??   How to using SUM() & GROUP BY