Error (Ora-00923: from Keyword Not Found Where Expected)

Check reserved words. This was my issue. For whatever reason using "size" as a column alias caused oracle to spit that exact error out and it had me scratching my head for a while.

select 1 size, 1 id from dual

You may try doing this:-

select 
  country_olympic_name, 
  SUM(part_gold) as "Number of Gold Medals"
From
  games.country,
  games.participation
where
  participation.country_isocode = country.country_isocode
group by
  country_olympic_name;

Try this...

SELECT
      COUNTRY_OLYMPIC_NAME,
      SUM ( PART_GOLD ) AS NUMBER_OF_GOLD_MEDALS
FROM
      GAMES.COUNTRY,
      GAMES.PARTICIPATION
WHERE
      PARTICIPATION.COUNTRY_ISOCODE = COUNTRY.COUNTRY_ISOCODE
GROUP BY
      COUNTRY_OLYMPIC_NAME;

In my case, I had this query

SELECT BANK_NAME
DECODE (SWIFT_CODE, 'BRDEROBU', 'BRD',
                   'NO RESULT') RESULT
FROM BANK_GAR;

As you may see, I didn't had the comma after the SELECT BANK_NAME line.

The correct query is:

SELECT BANK_NAME,
DECODE (SWIFT_CODE, 'BRDEROBU', 'BRD',
                   'NO RESULT') RESULT
FROM BANK_GAR;