removing duplicates in sql select query code example

Example 1: sql delete duplicate

-- Oracle
DELETE films
WHERE rowid NOT IN (
    SELECT min(rowid)
    FROM films
    GROUP BY title, uk_release_date
);

Example 2: query delete duplicates

DELETE FROM dups a USING (
      SELECT MIN(ctid) as ctid, key
        FROM dups 
        GROUP BY key HAVING COUNT(*) > 1
      ) b
      WHERE a.key = b.key 
      AND a.ctid <> b.ctid