database - SQL not a single group group function error

Question

I am having a hard time getting my oracle developer query to output correctly. When I have the avg function in it, it gives me not a single group group error. When I take it out it works fine. I have tried using group by instead of order by but then it tells me that its not a group by expression.

SELECT LGBRAND.BRAND_ID, LGBRAND.BRAND_NAME, AVG(LGPRODUCT.PROD_PRICE)AS AVGER
FROM LGPRODUCT, LGBRAND
WHERE LGPRODUCT.BRAND_ID = LGBRAND.BRAND_ID
ORDER BY BRAND_NAME;

Answer 1

When you include an aggregate function (like avg, sum) in your query, you must group by all columns you aren't aggregating.

SELECT LGBRAND.BRAND_ID, LGBRAND.BRAND_NAME, AVG(LGPRODUCT.PROD_PRICE)AS AVGER
FROM LGPRODUCT, LGBRAND
WHERE LGPRODUCT.BRAND_ID = LGBRAND.BRAND_ID
GROUP BY
LGBRAND.BRAND_ID,
LGBRAND.BRAND_NAME
ORDER BY BRAND_NAME