Using DISTINCT for specific columns

Question

select distinct  employee_id, first_name,  commission_pct, department_id from
employees;

When I use the above query it results in distinct combination

Answer 1

Can you try this one?

SELECT
  NAME1,
  PH
FROM
      (WITH T
           AS (SELECT
                    'mark' NAME1,
                    '1234567' PH
              FROM
                    DUAL
              UNION ALL
              SELECT
                    'bailey',
                    '456789'
              FROM
                    DUAL
              UNION ALL
              SELECT
                    'mark',
                    '987654'
              FROM
                    DUAL)
       SELECT
            NAME1,
            PH,
            ROW_NUMBER ( ) OVER (PARTITION BY NAME1 ORDER BY NAME1) SEQ
       FROM
            T)
WHERE
      SEQ = 1;

If you dont care on a specific row, then use aggregate functions

SELECT
      NAME1,
      MAX ( PH ) PH
FROM
      T
GROUP BY
      NAME1;