Oracle 23c

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ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS';
ALTER SESSION SET NLS_TIMESTAMP_FORMAT = 'YYYY-MM-DD HH24:MI:SS.FF';
CREATE TABLE table_name (a, b) AS
SELECT 1, 1 FROM DUAL CONNECT BY LEVEL <= 3 UNION ALL
SELECT 1, 2 FROM DUAL CONNECT BY LEVEL <= 4 UNION ALL
SELECT 2, 1 FROM DUAL CONNECT BY LEVEL <= 2 UNION ALL
SELECT 2, 2 FROM DUAL CONNECT BY LEVEL <= 5;
14 rows affected

DECLARE
  PROCEDURE print_distinct_values
  IS
  BEGIN
    FOR r IN (SELECT DISTINCT * FROM table_name) LOOP
      DBMS_OUTPUT.PUT_LINE(r.a || ', ' || r.b);
    END LOOP;
  END;
BEGIN
  print_distinct_values();
END;
/
1 rows affected

dbms_output:
1, 1
1, 2
2, 1
2, 2

SELECT a, b FROM table_name GROUP BY a, b


A
B


1
1

1
2

2
1

2
2


SELECT a, b
FROM   table_name
ORDER BY ROW_NUMBER() OVER (PARTITION BY a, b ORDER BY ROWNUM)
FETCH FIRST ROW WITH TIES


A
B


1
1

1
2

2
1

2
2


SELECT a, b
FROM   (
  SELECT a, b,
         ROW_NUMBER() OVER (PARTITION BY a, b ORDER BY ROWNUM) AS rn
  FROM   table_name
)
WHERE  rn = 1


A
B


1
1

1
2

2
1

2
2