Delete duplicate rows from table with no unique key

Question

How do I delete duplicates rows in Postgres 9 table, the rows are completely duplicates on every field AND there is no individual field that could be used as a unique key so

Answer 1

Since you also need to avoid duplicates in the future, you could add a surrogate key and a unique constraint while dedupping:

---

-- add surrogate key
ALTER TABLE releases_labels
        ADD column id SERIAL NOT NULL PRIMARY KEY
        ;

-- verify
SELECT * FROM releases_labels;

DELETE FROM releases_labels dd
WHERE EXISTS (SELECT *
        FROM releases_labels x
        WHERE x.label = dd.label
        AND x.release_id = dd.release_id
        AND x.catno = dd.catno
        AND x.id < dd.id
        );

-- verify
SELECT * FROM releases_labels;

-- add unique constraint for the natural key
ALTER TABLE releases_labels
        ADD UNIQUE (label,release_id,catno)
        ;

-- verify
SELECT * FROM releases_labels;