Удаление дубликатов из таблицы

CREATE TABLE t (a INTEGER, b INTEGER);

ROLLBACK;
BEGIN;
CREATE TEMP TABLE tmp_tbl_test(a INT,b INT);
INSERT INTO tmp_tbl_test(a,b)
VALUES
(1,1),
(2,2),
(2,2),
(3,3),
(3,3),
(3,3),
(3,0);
WITH 
    tbl_d(a,b) AS(DELETE FROM tmp_tbl_test RETURNING *),
    tbl_i(a,b) AS(INSERT INTO tmp_tbl_test(a,b) SELECT DISTINCT a,b FROM tbl_d RETURNING *)
SELECT a,b FROM tbl_i;
SELECT * FROM tmp_tbl_test;
DROP TABLE tmp_tbl_test;
COMMIT;

WITH 
    tbl_d(a,b) AS(DELETE FROM tmp_tbl_test RETURNING *),
    tbl_i(a,b) AS(INSERT INTO tmp_tbl_test(a,b) SELECT DISTINCT a,b FROM tbl_d RETURNING *)
SELECT a,b FROM tbl_i;

SELECT* FROM t2del;
SELECT ctid, * FROM t2del;
 
SELECT DISTINCT a, b
FROM t2del;
 
SELECT a, b
FROM t2del;
GROUP BY a, b;

WITH del 
AS (
    DELETE
    FROM t2del
    RETURNING a, b 
    )
INSERT INTO t2del
SELECT DISTINCT a, b
FROM del;
 
SELECT* FROM t2del;

SELECT
    a,
    b,
    COUNT(*)
FROM
    t 
GROUP BY
    a,
    b
HAVING COUNT(*) > 1;

DELETE FROM t
WHERE (a, b) IN (
    SELECT
        a,
        b
    FROM
        t 
    GROUP BY
        a,
        b
    HAVING COUNT(*) > 1
);

DELETE FROM t t1
USING t t2
WHERE
    t1.ctid < t2.ctid
AND t1.a = t2.a
AND t1.b = t2.b;